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模型定义参考
Chapter 5 explains the basics of defining models, and we use them throughout the rest of the book. There is, however, a huge range of model options available not covered elsewhere. This appendix explains each possible model definition option.
第五章解释了定义模式的基本方式，并且我们在整本书都用到了它们。然而，有相当数量的模型选项我们没有提到过。这个附录解释了每个可能的模型定义选项。
Note that although these APIs are considered very stable, the Django developers consistently add new shortcuts and conveniences to the model definition. Its a good idea to always check the latest documentation online at http://www.djangoproject.com/documentation/0.96/model-api/.
注意，虽然这些API被认作是非常稳定的，不过Django的开发者们会一贯地保持将新的快捷和方便加入到模型定义中。经常检查最新的在线文档是个好主意： http://www.djangoproject.com/documentation/0.96/model-api/ 。
The most important part of a model and the only required part of a model is the list of database fields it defines.
一个模型最重要也是唯一必需的部分，是它定义的数据库字段。
Field Name Restrictions
字段名称限制
Django places only two restrictions on model field names:
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A field name cannot be a Python reserved word, because that would result in a Python syntax error, for example:
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class Example(models.Model):
pass = models.IntegerField() # 'pass' is a reserved word!
A field name cannot contain more than one underscore in a row, due to the way Djangos query lookup syntax works, for example:
一个字段名不能包含连续的一个以上的下划线，因为那是Django查询语句的语法。例如：
class Example(models.Model):
foo__bar = models.IntegerField() # 'foo__bar' has two underscores!
These limitations can be worked around, though, because your field name doesnt necessarily have to match your database column name. See db_column, below. below.
不过这些限制可以被绕过，因为字段名不一定要和数据库列名称完全相同。参见下面的 db_column 。
SQL reserved words, such as join , where , or select , are allowed as model field names, because Django escapes all database table names and column names in every underlying SQL query. It uses the quoting syntax of your particular database engine.
SQL保留字，像 join 、 where 或 select ， 可以 用在模型字段名中，因为Django在每个SQL查询中，会对所有的数据库表名称和列名称进行转义。它会根据不同的数据库引擎的引用语法来进行相应的转义。
Each field in your model should be an instance of the appropriate Field class. Django uses the field class types to determine a few things:
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The database column type (e.g., INTEGER , VARCHAR ).
数据库列类型（如 INTEGER 、 VARCHAR ）。
The widget to use in Djangos admin interface, if you care to use it (e.g., <input type="text"> , <select> ).
在Django的admin界面中使用的部件，如果你想要指定的话。（例如： <input type="text"> 、 <select> ）。
The minimal validation requirements, which are used in Djangos admin interface.
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A complete list of field classes follows, sorted alphabetically. Note that relationship fields (ForeignKey , etc.) are handled in the next section.
下面是一个完整的按照字母排序的字段列表。注意关系字段（ ForeignKey 等）会在下一节里说明。
An IntegerField that automatically increments according to available IDs. You usually wont need to use this directly; a primary key field will automatically be added to your model if you dont specify otherwise.
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A true/false field.
一个真／假（true/false）字段。
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A string field, for small- to large-sized strings. For large amounts of text, use TextField .
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CharField has an extra required argument, maxlength , which is the maximum length (in characters) of the field. This maximum length is enforced at the database level and in Djangos validation.
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A field of integers separated by commas. As in CharField , the maxlength argument is required.
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A date field. DateField has a few extra optional arguments, as shown in Table B-1.
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| Argument | Description |
|---|---|
| auto_now | Automatically sets the field to now every time the object is saved. Its useful for last-modified timestamps. Note that the current date is always used; its not just a default value that you can override. |
| auto_now_add | Automatically sets the field to now when the object is first created. Its useful for creation of timestamps. Note that the current date is always used; its not just a default value that you can override. |
| Argument | Description |
|---|---|
| auto_now | 每次对象保存时，自动设置为当前日期。一般用来产生最后一次修改时间。 注意：使用此选项的字段的值总是在保存时被设置为保存时的日期，这是无法改变的。 |
| auto_now_add | 当对象第一次产生时字段设置为当前日期。一般用来产生对象的建立时间。 注意：使用此选项的字段值总是在对象建立时被设置为建立时的日期，这是无法改变的。 |
A date and time field. It takes the same extra options as DateField .
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A CharField that checks that the value is a valid email address. This doesnt accept maxlength ; its maxlength is automatically set to 75.
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A file-upload field. It has one required argument, as shown in Table B-3.
文件上传区域。它必须有一个表B-3所显示的参数。
| Argument | Description |
|---|---|
| upload_to | A local filesystem path that will be appended to your MEDIA_ROOT setting to determine the output of the get_<fieldname>_url() helper function |
| 参数 | 描述 |
|---|---|
| upload_to | 一个本地的文件系统路径，被附加到你的 MEDIA_ROOT 设置后面，这决定了 get_<fieldname>_url() 辅助函数的输出 |
This path may contain strftime formatting (see http://www.djangoproject.com/r/python/strftime/), which will be replaced by the date/time of the file upload (so that uploaded files dont fill up the given directory).
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Using a FileField or an ImageField in a model takes a few steps:
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In your settings file, youll need to define MEDIA_ROOT as the full path to a directory where youd like Django to store uploaded files. (For performance, these files are not stored in the database.) Define MEDIA_URL as the base public URL of that directory. Make sure that this directory is writable by the Web servers user account.
在settings文件中你需要定义 MEDIA_ROOT ，它就是你要保存上传文件的目录的全路径。（出于性能考虑，这些文件不会保存到数据库中。）还要定义 MEDIA_URL ，刚才那个目录的对外URL。你要确保网络服务器使用的用户对这个目录是可写入的。
Add the FileField or ImageField to your model, making sure to define the upload_to option to tell Django to which subdirectory of MEDIA_ROOT it should upload files.
在模型中添加 FileField 或者 ImageField ，务必要定义 upload_to 选项，这样Django才知道把上传的文件写到 MEDIA_ROOT 的哪个子目录中。
All that will be stored in your database is a path to the file (relative to MEDIA_ROOT ). Youll most likely want to use the convenience get_<fieldname>_url function provided by Django. For example, if your ImageField is called mug_shot , you can get the absolute URL to your image in a template with {{ object.get_mug_shot_url }} .
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For example, say your MEDIA_ROOT is set to '/home/media' , and upload_to is set to 'photos/%Y/%m/%d' . The '%Y/%m/%d' part of upload_to is strftime formatting; '%Y' is the four-digit year, '%m' is the two-digit month, and '%d' is the two-digit day. If you upload a file on January 15, 2007, it will be saved in the directory /home/media/photos/2007/01/15 .
例如,你的 MEDIA_ROOT 设置为 '/home/media' ， upload_to 设置为 'photos/%Y/%m/%d' 。其中 '%Y/%m/%d' 部分是日期格式化串： '%Y' 为4位的年份， '%m' 是两位月份， '%d' 是两位的日期。如果你在2007年1月15日上传文件，这个文件就会被保存在 /home/media/photos/2007/01/15 目录下。
If you want to retrieve the upload files on-disk file name, or a URL that refers to that file, or the files size, you can use the get_FIELD_filename() , get_FIELD_url() , and get_FIELD_size() methods. See Appendix C for a complete explanation of these methods.
如果你想得到上传文件在磁盘上的文件名，或者指向该文件的URL，或者文件大小，你可以分别使用这些方法： get_FIELD_filename() 、 get_FIELD_url() 和 get_FIELD_size() 。附录C中有这些方法的详细解释。
Note
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Whenever you deal with uploaded files, you should pay close attention to where youre uploading them and what type of files they are, to avoid security holes. Validate all uploaded files so that youre sure the files are what you think they are.
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For example, if you blindly let somebody upload files, without validation, to a directory thats within your Web servers document root, then somebody could upload a CGI or PHP script and execute that script by visiting its URL on your site. Dont let that happen!
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A field whose choices are limited to the file names in a certain directory on the filesystem. It has three special arguments, as shown in Table B-4.
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| Argument | Description |
|---|---|
| path | Required ; the absolute filesystem path to a directory from which this FilePathField should get its choices (e.g., "/home/images" ). |
| match | Optional; a regular expression, as a string, that FilePathField will use to filter file names. Note that the regex will be applied to the base file name, not the full path (e.g., "foo.*\.txt^" , which will match a file called foo23.txt , but not bar.txt or foo23.gif ). |
| recursive | Optional; either True or False . The default is False . It specifies whether all subdirectories of path should be included. |
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Of course, these arguments can be used together.
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The one potential gotcha is that match applies to the base file name, not the full path. So, this example:
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FilePathField(path="/home/images", match="foo.*", recursive=True)
will match /home/images/foo.gif but not /home/images/foo/bar.gif because the match applies to the base file name (foo.gif and bar.gif ).
会匹配 /home/images/foo.gif ，但是不会匹配 /home/images/foo/bar.gif ，因为 match 只作用于基文件名（ foo.gif 和 bar.gif ）。
A floating-pint number, represented in Python by a float instance. It has two required arguments, as shown in Table B-2.
一个浮点数，对应Python中的 float 实例。它有两个 必需 的参数，如表B-4所示。
| Argument | Description |
|---|---|
| max_digits | The maximum number of digits allowed in the number |
| decimal_places | The number of decimal places to store with the number |
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For example, to store numbers up to 999 with a resolution of two decimal places, youd use the following:
例如，要保存最大值为999并且有两位小数的数字，应该这样写：
models.FloatField(..., max_digits=5, decimal_places=2)
And to store numbers up to approximately 1 billion with a resolution of ten decimal places, you would use this:
要保存最大值为10亿并且带10个小数位的数字，要这样写：
models.FloatField(..., max_digits=19, decimal_places=10)
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Like FileField , but validates that the uploaded object is a valid image. It has two extra optional arguments, height_field and width_field , which, if set, will be autopopulated with the height and width of the image each time a model instance is saved.
像 FileField 一样，只不过要验证上传的对象是一个有效的图片。它有两个额外的可选参数： height_field 和 width_field ，如果设置了的话，每当模型实例被保存的时候，这两个值就会被设置成图片的高度和宽度。
In addition to the special get_FIELD_* methods that are available for FileField , an ImageField also has get_FIELD_height() and get_FIELD_width() methods. These are documented in Appendix C.
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ImageField requires the Python Imaging Library (http://www.pythonware.com/products/pil/).
ImageField 依赖Python图片库（ http://www.pythonware.com/products/pil/ ）。
An integer.
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An IP address, in string format (e.g., "24.124.1.30" ).
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Like a BooleanField , but allows None /NULL as one of the options. Use this instead of a BooleanField with null=True .
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A CharField that checks that the value is a valid U.S.-style phone number (in the format XXX-XXX-XXXX ).
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Note
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If you need to represent a phone number from another country, check the django.contrib.localflavor package to see if field definitions for your country are included.
如果你需要表示一个其他国家的电话号码，检查 django.contrib.localflavor 包，看看是否包括对应你的国家的字段定义。
Like an IntegerField , but must be positive.
和 IntegerField 类似，但必须是正值。
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Like a PositiveIntegerField , but only allows values under a certain point. The maximum value allowed by these fields is database dependent, but since databases have a 2-byte small integer field, the maximum positive small integer is usually 65,535.
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Slug is a newspaper term. A slug is a short label for something, containing only letters, numbers, underscores, or hyphens. Theyre generally used in URLs.
嵌条是报纸业的术语。 嵌条 就是一段内容的简短标签，这段内容只能包含字母、数字、下划线或连字符。通常用于URL中。
Like a CharField , you can specify maxlength . If maxlength is not specified, Django will use a default length of 50.
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A SlugField implies db_index=True since slugs are primarily used for database lookups.
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SlugField accepts an extra option, prepopulate_from , which is a list of fields from which to autopopulate the slug, via JavaScript, in the objects admin form:
SlugField 接受一个额外的选项： prepopulate_from ，它是一些字段的列表，而这些字段将在对象管理表单中通过JavaScript生成嵌条。
models.SlugField(prepopulate_fpom=("pre_name", "name"))
prepopulate_from doesnt accept DateTimeField names as arguments.
prepopulate_from 不接受 DateTimeField 字段的名字作为参数。
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Like an IntegerField , but only allows values in a certain database-dependent range (usually -32,768 to +32,767).
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An unlimited-length text field.
一个不限长度的文字字段。
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A time of day. It accepts the same autopopulation options as DateField and DateTimeField .
时分秒的时间显示。它接受的可指定参数与 DateField 和 DateTimeField 相同。
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A field for a URL. If the verify_exists option is True (the default), the URL given will be checked for existence (i.e., the URL actually loads and doesnt give a 404 response).
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Like other character fields, URLField takes the maxlength argument. If you dont specify maxlength , a default of 200 is used.
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A two-letter U.S. state abbreviation.
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Note
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If you need to represent other countries or states, look first in the django.contrib.localflavor package to see if Django already includes fields for your locale.
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A TextField that checks that the value is valid XML that matches a given schema. It takes one required argument, schema_path , which is the filesystem path to a RELAX NG (http://www.relaxng.org/) schema against which to validate the field.
它就是一个 TextField ，只不过要检查值是匹配指定schema的合法XML。它有一个必需参数： schema_path ，它是验证字段合法性所需的RELAX NG（ http://www.relaxng.org/ ）schema的物理路径。
Requires jing (http://thaiopensource.com/relaxng/jing.html) to validate the XML.
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The following arguments are available to all field types. All are optional.
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If True , Django will store empty values as NULL in the database. The default is False .
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Note that empty string values will always get stored as empty strings, not as NULL . Only use null=True for nonstring fields such as integers, Booleans, and dates. For both types of fields, you will also need to set blank=True if you wish to permit empty values in forms, as the null parameter only affects database storage (see the following section, titled blank).
记住，空字符串值保存时总是以空字符串的形式存在，而不是 NULL 。一般只对非字符串字段使用 null=True ，比如整型、布尔型和日期型。对于这两种字段，如果你允许表单中的对应值为空的话，你还需要设定 blank=True ，因为 null 参数只影响数据库存储（参见下面题为blank的一节）。
Avoid using null on string-based fields such as CharField and TextField unless you have an excellent reason. If a string-based field has null=True , that means it has two possible values for no data: NULL and the empty string. In most cases, its redundant to have two possible values for no data; Djangos convention is to use the empty string, not NULL .
如果没有充分理由的话，应该尽量避免对诸如 CharField 和 TextField 这样字符串字段使用 null 参数。如果对字符串字段指定了 null=True 的话，这意味着空数据有两种可能的值： NULL 和空字符串。而大多数情况下，空数据没必要对应两种可能的值，所以Django中习惯使用空字符串，而不是 NULL 。
If True , the field is allowed to be blank. The default is False .
如果是 True ，该字段允许留空，默认为 False 。
Note that this is different from null . null is purely database related, whereas blank is validation related. If a field has blank=True , validation on Djangos admin site will allow entry of an empty value. If a field has blank=False , the field will be required.
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An iterable (e.g., a list, tuple, or other iterable Python object) of two tuples to use as choices for this field.
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If this is given, Djangos admin interface will use a select box instead of the standard text field and will limit choices to the choices given.
如果指定了这个选项，Django管理界面不会使用标准的文本框了，而是取而代之，使用列表选择框限定选择范围。
A choices list looks like this:
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YEAR_IN_SCHOOL_CHOICES = (
('FR', 'Freshman'),
('SO', 'Sophomore'),
('JR', 'Junior'),
('SR', 'Senior'),
('GR', 'Graduate'),
)
The first element in each tuple is the actual value to be stored. The second element is the human-readable name for the option.
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The choices list can be defined either as part of your model class:
选项列表既可以作为模型类的一部分来定义：
class Foo(models.Model):
GENDER_CHOICES = (
('M', 'Male'),
('F', 'Female'),
)
gender = models.CharField(maxlength=1, choices=GENDER_CHOICES)
or outside your model class altogether:
也可以定义到模型类的外面：
GENDER_CHOICES = (
('M', 'Male'),
('F', 'Female'),
)
class Foo(models.Model):
gender = models.CharField(maxlength=1, choices=GENDER_CHOICES)
For each model field that has choices set, Django will add a method to retrieve the human-readable name for the fields current value. See Appendix C for more details.
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The name of the database column to use for this field. If this isnt given, Django will use the fields name. This is useful when youre defining a model around a database that already exists.
当前字段在数据库中对应的列的名字。如果没有指定的话，Django会使用这个字段的名字。当你要定义一个数据库中存在命名冲突的模型时，这个选项非常有用。
If your database column name is an SQL reserved word, or if it contains characters that arent allowed in Python variable names (notably the hyphen), thats OK. Django quotes column and table names behind the scenes.
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If True , Django will create a database index on this column when creating the table (i.e., when running manage.py syncdb ). ta default -
如果为 True ，Django会在创建表格（比如运行 manage.py syncdb ）时对这一列创建数据库索引。
The default value for the field.
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If False , the field will not be editable in the admin interface or via form processing. The default is True .
如果为 False ，这个字段在管理界面或表单里将不能编辑。默认为 True 。
Extra help text to be displayed under the field on the objects admin form. Its useful for documentation even if your object doesnt have an admin form.
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If True , this field is the primary key for the model.
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If you dont specify primary_key=True for any fields in your model, Django will automatically add this field:
如果你没有对模型中的任何字段指定 primary_key=True 的话，Django会自动添加这个字段：
id = models.AutoField('ID', primary_key=True)
Thus, you dont need to set primary_key=True on any of your fields unless you want to override the default primary-key behavior.
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primary_key=True implies blank=False , null=False , and unique=True . Only one primary key is allowed on an object.
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By default, Djangos admin uses a select-box interface (<select>) for fields that are ForeignKey or have choices set. If radio_admin is set to True , Django will use a radio-button interface instead.
默认地，对于 ForeignKey 或者拥有 choices 设置的字段，Django管理界面会使用列表选择框（<select>）。如果 radio_admin 设置为 True 的话，Django就会使用单选按钮界面。
Dont use this for a field unless its a ForeignKey or has choices set.
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If True , the value for this field must be unique throughout the table.
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Set to the name of a DateField or DateTimeField to require that this field be unique for the value of the date field, for example:
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class Story(models.Model):
pub_date = models.DateTimeField()
slug = models.SlugField(unique_for_date="pub_date")
...
In the preceding code, Django wont allow the creation of two stories with the same slug published on the same date. This differs from using a unique_together constraint in that only the date of the pub_date field is taken into account; the time doesnt matter.
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Like unique_for_date , but requires the field to be unique with respect to the month of the given field.
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Like unique_for_date and unique_for_month , but for an entire year.
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Each field type, except for ForeignKey , ManyToManyField , and OneToOneField , takes an optional first positional argument a verbose name. If the verbose name isnt given, Django will automatically create it using the fields attribute name, converting underscores to spaces.
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In this example, the verbose name is "Person's first name" :
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first_name = models.CharField("Person's first name", maxlength=30)
In this example, the verbose name is "first name" :
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first_name = models.CharField(maxlength=30)
ForeignKey , ManyToManyField , and OneToOneField require the first argument to be a model class, so use the verbose_name keyword argument:
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poll = models.ForeignKey(Poll, verbose_name="the related poll") sites = models.ManyToManyField(Site, verbose_name="list of sites") place = models.OneToOneField(Place, verbose_name="related place")
The convention is not to capitalize the first letter of the verbose_name . Django will automatically capitalize the first letter where it needs to.
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Clearly, the power of relational databases lies in relating tables to each other. Django offers ways to define the three most common types of database relationships: many-to-one, many-to-many, and one-to-one.
很明显，关系数据库的强大在于表与表之间的相互关联关系,Django提供定义了三种最为通用的数库库关系类型：many-to-one(多对一关系),many-to-many(多对多关系)和one-to-one(一对一关系)
However, the semantics of one-to-one relationships are being revisited as this book goes to print, so theyre not covered in this section. Check the online documentation for the latest information.
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To define a many-to-one relationship, use ForeignKey . You use it just like any other Field type: by including it as a class attribute of your model.
用 ForeignKey 来定义多对一的关系。用法和其他的 Field 是一样的，把它放到模型中类的属性定义中就行了。
ForeignKey requires a positional argument: the class to which the model is related.
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For example, if a Car model has a Manufacturer that is, a Manufacturer makes multiple cars but each Car only has one Manufacturer use the following definitions:
例如，一个 Car 模型中有个 Manufacturer ，就是说一个 Manufacturer 可以生产很多汽车，但是每个 Car 只能有一个 Manufacturer ，可以这样定义：
class Manufacturer(models.Model):
...
class Car(models.Model):
manufacturer = models.ForeignKey(Manufacturer)
...
To create a recursive relationship an object that has a many-to-one relationship with itself use models.ForeignKey('self') :
要建立一个 递归 的关系——就是一个对象和自身有多对一的关系——可以这样写： models.ForeignKey('self') ：
class Employee(models.Model):
manager = models.ForeignKey('self')
If you need to create a relationship on a model that has not yet been defined, you can use the name of the model, rather than the model object itself:
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class Car(models.Model):
manufacturer = models.ForeignKey('Manufacturer')
...
class Manufacturer(models.Model):
...
Note, however, that you can only use strings to refer to models in the same models.py file you cannot use a string to reference a model in a different application, or to reference a model that has been imported from elsewhere.
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Behind the scenes, Django appends "_id" to the field name to create its database column name. In the preceding example, the database table for the Car model will have a manufacturer_id column. (You can change this explicitly by specifying db_column ; see the earlier db_column section.) However, your code should never have to deal with the database column name, unless you write custom SQL. Youll always deal with the field names of your model object.
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Its suggested, but not required, that the name of a ForeignKey field (manufacturer in the example) be the name of the model, in lowercase letters. You can, of course, call the field whatever you want, for example:
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class Car(models.Model):
company_that_makes_it = models.ForeignKey(Manufacturer)
# ...
ForeignKey fields take a number of extra arguments for defining how the relationship should work (see Table B-5). All are optional.
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| Argument | Description |
|---|---|
| edit_inline | If not False , this related object is edited inline on the related objects page. This means that the object will not have its own admin interface. Use either models.TABULAR or models.STACKED , which, respectively, designate whether the inline-editable objects are displayed as a table or as a stack of fieldsets. |
| limit_choices_to | A dictionary of lookup arguments and values (see Appendix C) that limit the available admin choices for this object. Use this with functions from the Python datetime module to limit choices of objects by date. For example, the following:
limit_choices_to = {'pub_date__lte': datetime.now}
only allows the choice of related objects with a pub_date before the current date/time to be chosen. Instead of a dictionary, this can be a Q object (see Appendix C) for more complex queries. This is not compatible with edit_inline . |
| max_num_in_admin | For inline-edited objects, this is the maximum number of related objects to display in the admin interface. Thus, if a pizza could have only up to ten toppings, max_num_in_admin=10 would ensure that a user never enters more than ten toppings. Note that this doesnt ensure more than ten related toppings ever get created. It simply controls the admin interface; it doesnt enforce things at the Python API level or database level. |
| min_num_in_admin | The minimum number of related objects displayed in the admin interface. Normally, at the creation stage, num_in_admin inline objects are shown, and at the edit stage, num_extra_on_change blank objects are shown in addition to all pre-existing related objects. However, no fewer than min_num_in_admin related objects will ever be displayed. |
| num_extra_on_change | The number of extra blank related-object fields to show at the change stage. |
| num_in_admin | The default number of inline objects to display on the object page at the add stage. |
| raw_id_admin | Only display a field for the integer to be entered instead of a drop-down menu. This is useful when related to an object type that will have too many rows to make a select box practical. This is not used with edit_inline . |
| related_name | The name to use for the relation from the related object back to this one. See Appendix C for more information. |
| to_field | The field on the related object that the relation is to. By default, Django uses the primary key of the related object. |
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To define a many-to-many relationship, use ManyToManyField . Like ForeignKey , ManyToManyField requires a positional argument: the class to which the model is related.
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For example, if a Pizza has multiple Topping objects that is, a Topping can be on multiple pizzas and each Pizza has multiple toppings heres how youd represent that:
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class Topping(models.Model):
...
class Pizza(models.Model):
toppings = models.ManyToManyField(Topping)
...
As with ForeignKey , a relationship to self can be defined by using the string 'self' instead of the model name, and you can refer to as-yet undefined models by using a string containing the model name. However, you can only use strings to refer to models in the same models.py file you cannot use a string to reference a model in a different application, or to reference a model that has been imported from elsewhere.
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Its suggested, but not required, that the name of a ManyToManyField (toppings in the example) be a plural term describing the set of related model objects.
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Behind the scenes, Django creates an intermediary join table to represent the many-to-many relationship.
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It doesnt matter which model gets the ManyToManyField , but you need it in only one of the models not in both.
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If youre using the admin interface, ManyToManyField instances should go in the object thats going to be edited in the admin interface. In the preceding example, toppings is in Pizza (rather than Topping having a pizzas ManyToManyField ) because its more natural to think about a Pizza having toppings than a topping being on multiple pizzas. The way its set up in the example, the Pizza admin form would let users select the toppings.
如果你是用管理界面的话， ManyToManyField 实例应该放到要在管理界面编辑的对象里。在前面的例子里，是 toppings 位于 Pizza 中的（而不是 Topping 中有一个名为 pizzas 的 ManyToManyField ），因为这样比一种配料放到多个披萨中更符合人们的思维习惯。在这个例子中，用户可以在 Pizza 的管理界面中选择配料。
ManyToManyField objects take a number of extra arguments for defining how the relationship should work (see Table B-6). All are optional.
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| Argument | Description |
|---|---|
| related_name | The name to use for the relation from the related object back to this one. See Appendix C for more information. |
| filter_interface | Use a nifty, unobtrusive JavaScript filter interface instead of the usability-challenged <select multiple> in the admin form for this object. The value should be models.HORIZONTAL or models.VERTICAL (i.e., should the interface be stacked horizontally or vertically). |
| limit_choices_to | See the description under ForeignKey . |
| symmetrical | Only used in the definition of ManyToManyField on self. Consider the following model:
class Person(models.Model):
friends = models.ManyToManyField("self")
When Django processes this model, it identifies that it has a ManyToManyField on itself, and as a result, it doesnt add a person_set attribute to the Person class. Instead, the ManyToManyField is assumed to be symmetrical that is, if I am your friend, then you are my friend. If you do not want symmetry in ManyToMany relationships with self , set symmetrical to False . This will force Django to add the descriptor for the reverse relationship, allowing ManyToMany relationships to be nonsymmetrical. |
| db_table | The name of the table to create for storing the many-to-many data. If this is not provided, Django will assume a default name based upon the names of the two tables being joined. |
| 参数 | 描述 |
|---|---|
| related_name | 关联对象反向引用描述符。更多信息参见附录C。 |
| filter_interface | 在这个对象的管理界面里面，使用简单易用的JavaScript过滤界面，而不是使用可用性较差的 <select multiple> 。它的值应该是 models.HORIZONTAL 或者 models.VERTICAL （就是说界面应该横放还是竖放）。 |
| limit_choices_to | 参见 ForeignKey 中对本项的描述。 |
| symmetrical | 仅用于模型定义指向自身的 ManyToManyField 的情况。看下面这个模型：
class Person(models.Model):
friends = models.ManyToManyField("self")
当Django处理这个模型时，会发现它有一个指向自身的 ManyToManyField ，它因此就不会在 Person 类中添加 person_set 属性。而对于 ManyToManyField ，我们会假定这种 关系是对称的，就是说，如果我是你的朋友，你也是我的朋友。 在对 self 的 ManyToMany 关系中，如果你不需要这种对称性，你可以把 symmetrical 的值设为 False 。这样就会强制Django给关系的另外一方添加描述符， 从而使这种关系不是对称的。 |
| db_table | 用来保存多对多数据的表的名字。如果没有提供本项的话，Django会把两个表的名字连接起来当 做多对多数据表的默认名字。 |
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Model-specific metadata lives in a class Meta defined in the body of your model class:
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class Book(models.Model):
title = models.CharField(maxlength=100)
class Meta:
# model metadata options go here
...
Model metadata is anything thats not a field, such as ordering options and so forth.
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The sections that follow present a list of all possible Meta options. No options are required. Adding class Meta to a model is completely optional.
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The name of the database table to use for the model.
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To save you time, Django automatically derives the name of the database table from the name of your model class and the application that contains it. A models database table name is constructed by joining the models app label the name you used in manage.py startapp to the models class name, with an underscore between them.
为了节省时间，Django通过你定义的模型的类名和所在的应用程序的名称自动得到数据库的表名，它是由模型的应用程序名称——就是你执行 manage.py startapp 命令所指定的应用程序的名称——和模型的类名组成的，它们之间通过下划线进行连接。
For example, if you have an application books (as created by manage.py startapp books ), a model defined as class Book will have a database table named books .
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To override the database table name, use the db_table parameter in class Meta :
通过复写 class Meta 中的 db_table 参数可以改变模型映射的数据库表名：
class Book(models.Model):
...
class Meta:
db_table = 'things_to_read'
If this isnt given, Django will use app_label + '_' + model_class_name . See the section Table Names for more information.
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If your database table name is an SQL reserved word, or it contains characters that arent allowed in Python variable names (notably the hyphen), thats OK. Django quotes column and table names behind the scenes.
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The name of a DateField or DateTimeField in the model. This specifies the default field to use in your model Manager s latest() method.
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Heres an example:
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class CustomerOrder(models.Model):
order_date = models.DateTimeField()
...
class Meta:
get_latest_by = "order_date"
See Appendix C for more information on the latest() method.
关于 latest() 方法的更多信息可参考附录C。
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Marks this object as orderable with respect to the given field. This is almost always used with related objects to allow them to be ordered with respect to a parent object. For example, if an Answer relates to a Question object, and a question has more than one answer, and the order of answers matters, youd do this:
标识这个对象可以根据指定字段排序，这个主要用于相互关联的对象，让他们可以按照和父对象相关的方式排序。例如，如果 Answer 和 Question 对象相关，同一个问题可能对应多个答案，如果答案顺序很重要的话，你应该这样做：
class Answer(models.Model):
question = models.ForeignKey(Question)
# ...
class Meta:
order_with_respect_to = 'question'
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The default ordering for the object, for use when obtaining lists of objects:
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class Book(models.Model):
title = models.CharField(maxlength=100)
class Meta:
ordering = ['title']
This is a tuple or list of strings. Each string is a field name with an optional - prefix, which indicates descending order. Fields without a leading - will be ordered ascending. Use the string "?" to order randomly.
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For example, to order by a title field in ascending order (i.e., A-Z), use this:
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ordering = ['title']
To order by title in descending order (i.e., Z-A), use this:
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ordering = ['-title']
To order by title in descending order, and then by title in ascending order, use this:
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ordering = ['-title', 'author']
Note that, regardless of how many fields are in ordering , the admin site uses only the first field.
注意，无论 ordering 中有多少字段，admin界面只使用第一个字段。
Extra permissions to enter into the permissions table when creating this object. Add, delete, and change permissions are automatically created for each object that has admin set. This example specifies an extra permission, can_deliver_pizzas :
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class Employee(models.Model):
...
class Meta:
permissions = (
("can_deliver_pizzas", "Can deliver pizzas"),
)
This is a list or tuple of two tuples in the format (permission_code, human_readable_permission_name) .
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See Chapter 12 for more on permissions.
有关权限的更多信息参见第12章。
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Sets of field names that, taken together, must be unique:
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class Employee(models.Model):
department = models.ForeignKey(Department)
extension = models.CharField(maxlength=10)
...
class Meta:
unique_together = [("department", "extension")]
This is a list of lists of fields that must be unique when considered together. Its used in the Django admin interface and is enforced at the database level (i.e., the appropriate UNIQUE statements are included in the CREATE TABLE statement).
这是一个由一些字段列表组成的列表，每个列表里的字段的组合值必须是唯一的。它用于Django管理界面，而且在数据库层是强制要求的（就是说在 CREATE TABLE 语句中会包含一些 UNIQUE 语句）。
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A human-readable name for the object, singular:
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class CustomerOrder(models.Model):
order_date = models.DateTimeField()
...
class Meta:
verbose_name = "order"
If this isnt given, Django will use a adapted version of the class name in which CamelCase becomes camel case .
如果没有给出此选项，那么Django将会根据类名来得到一个名称，例如 CamelCase 就会变成 camel case 。
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The plural name for the object:
对象复数形式的名字：
class Sphynx(models.Model):
...
class Meta:
verbose_name_plural = "sphynges"
If this isnt given, Django will add an s to the verbose_name .
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A Manager is the interface through which database query operations are provided to Django models. At least one Manager exists for every model in a Django application.
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The way Manager classes work is documented in Appendix C. This section specifically touches on model options that customize Manager behavior.
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By default, Django adds a Manager with the name objects to every Django model class. However, if you want to use objects as a field name, or if you want to use a name other than objects for the Manager , you can rename it on a per-model basis. To rename the Manager for a given class, define a class attribute of type models.Manager() on that model, for example:
Django默认会给每个模型添加一个叫做 objects 的 Manager 。如果你想把一个字段命名为 objects 的话，或者你不想把 Manager 命名为 objects ，你可以在每个模型里做修改。在模型里面定一个 models.Manager() 类型的类属性，就可以修改这个类的 Manager 的名字了，例如：
from django.db import models
class Person(models.Model):
...
people = models.Manager()
Using this example model, Person.objects will generate an AttributeError exception (since Person doesnt have a objects attribute), but Person.people.all() will provide a list of all Person objects.
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You can use a custom Manager in a particular model by extending the base Manager class and instantiating your custom Manager in your model.
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There are two reasons you might want to customize a Manager : to add extra Manager methods, and/or to modify the initial QuerySet the Manager returns.
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Adding extra Manager methods is the preferred way to add table-level functionality to your models. (For row-level functionality that is, functions that act on a single instance of a model object use model methods (see below), not custom Manager methods.)
增加附加的 Manager 方法是在模型中增加数据表级别的功能的首选方法。（对于行级别的功能——就是作用于模型的单个实例上的功能——要使用模型方法（下面有介绍），而不是定制的 Manager 方法。）
A custom Manager method can return anything you want. It doesnt have to return a QuerySet .
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For example, this custom Manager offers a method with_counts() , which returns a list of all OpinionPoll objects, each with an extra num_responses attribute that is the result of an aggregate query:
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from django.db import connection
class PollManager(models.Manager):
def with_counts(self):
cursor = connection.cursor()
cursor.execute("""
SELECT p.id, p.question, p.poll_date, COUNT(*)
FROM polls_opinionpoll p, polls_response r
WHERE p.id = r.poll_id
GROUP BY 1, 2, 3
ORDER BY 3 DESC""")
result_list = []
for row in cursor.fetchall():
p = self.model(id=row[0], question=row[1], poll_date=row[2])
p.num_responses = row[3]
result_list.append(p)
return result_list
class OpinionPoll(models.Model):
question = models.CharField(maxlength=200)
poll_date = models.DateField()
objects = PollManager()
class Response(models.Model):
poll = models.ForeignKey(Poll)
person_name = models.CharField(maxlength=50)
response = models.TextField()
With this example, youd use OpinionPoll.objects.with_counts() to return that list of OpinionPoll objects with num_responses attributes.
在这个例子中，你通过调用 OpinionPoll.objects.with_counts() 来返回的所有的 OpinionPoll 对象都拥有一个 num_responses 属性。
Another thing to note about this example is that Manager methods can access self.model to get the model class to which theyre attached.
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A Manager s base QuerySet returns all objects in the system. For example, using this model:
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class Book(models.Model):
title = models.CharField(maxlength=100)
author = models.CharField(maxlength=50)
the statement Book.objects.all() will return all books in the database.
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You can override the base QuerySet by overriding the Manager.get_query_set() method. get_query_set() should return a QuerySet with the properties you require.
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For example, the following model has two managers one that returns all objects, and one that returns only the books by Roald Dahl:
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# First, define the Manager subclass.
class DahlBookManager(models.Manager):
def get_query_set(self):
return super(DahlBookManager, self).get_query_set().filter(author='Roald Dahl')
# Then hook it into the Book model explicitly.
class Book(models.Model):
title = models.CharField(maxlength=100)
author = models.CharField(maxlength=50)
objects = models.Manager() # The default manager.
dahl_objects = DahlBookManager() # The Dahl-specific manager.
With this sample model, Book.objects.all() will return all books in the database, but Book.dahl_objects.all() will return only the ones written by Roald Dahl.
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Of course, because get_query_set() returns a QuerySet object, you can use filter() , exclude() , and all the other QuerySet methods on it. So these statements are all legal:
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Book.dahl_objects.all() Book.dahl_objects.filter(title='Matilda') Book.dahl_objects.count()
This example also points out another interesting technique: using multiple managers on the same model. You can attach as many Manager() instances to a model as youd like. This is an easy way to define common filters for your models. Heres an example:
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class MaleManager(models.Manager):
def get_query_set(self):
return super(MaleManager, self).get_query_set().filter(sex='M')
class FemaleManager(models.Manager):
def get_query_set(self):
return super(FemaleManager, self).get_query_set().filter(sex='F')
class Person(models.Model):
first_name = models.CharField(maxlength=50)
last_name = models.CharField(maxlength=50)
sex = models.CharField(maxlength=1, choices=(('M', 'Male'), ('F', 'Female')))
people = models.Manager()
men = MaleManager()
women = FemaleManager()
This example allows you to request Person.men.all() , Person.women.all() , and Person.people.all() , yielding predictable results.
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If you use custom Manager objects, take note that the first Manager Django encounters (in order by which theyre defined in the model) has a special status. Django interprets the first Manager defined in a class as the default Manager . Certain operations such as Djangos admin site use the default Manager to obtain lists of objects, so its generally a good idea for the first Manager to be relatively unfiltered. In the last example, the people Manager is defined first so its the default Manager .
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Define custom methods on a model to add custom row-level functionality to your objects. Whereas Manager methods are intended to do tablewide things, model methods should act on a particular model instance.
自定义model的方法可以为你的model对象提供行级的操作功能。Whereas Manager methods are intended to do tablewide things, model methods should act on a particular model instance.
This is a valuable technique for keeping business logic in one place: the model. For example, this model has a few custom methods:
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class Person(models.Model):
first_name = models.CharField(maxlength=50)
last_name = models.CharField(maxlength=50)
birth_date = models.DateField()
address = models.CharField(maxlength=100)
city = models.CharField(maxlength=50)
state = models.USStateField() # Yes, this is America-centric...
def baby_boomer_status(self):
"""Returns the person's baby-boomer status."""
import datetime
if datetime.date(1945, 8, 1) <= self.birth_date <= datetime.date(1964, 12, 31):
return "Baby boomer"
if self.birth_date < datetime.date(1945, 8, 1):
return "Pre-boomer"
return "Post-boomer"
def is_midwestern(self):
"""Returns True if this person is from the Midwest."""
return self.state in ('IL', 'WI', 'MI', 'IN', 'OH', 'IA', 'MO')
@property
def full_name(self):
"""Returns the person's full name."""
return '%s %s' % (self.first_name, self.last_name)
The last method in this example is a property an attribute implemented by custom getter/setter user code. Properties are a nifty trick added to Python 2.2; you can read more about them at http://www.python.org/download/releases/2.2/descrintro/#property.
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There are also a handful of model methods that have special meaning to Python or Django. These methods are described in the sections that follow.
還有一堆手動的模型方法，對Python or Django有特別的意義。 這些方法在下面的段落裏會描述。
__str__() is a Python magic method that defines what should be returned if you call str() on the object. Django uses str(obj) (or the related function, unicode(obj) , described shortly) in a number of places, most notably as the value displayed to render an object in the Django admin site and as the value inserted into a template when it displays an object. Thus, you should always return a nice, human-readable string for the objects __str__ . Although this isnt required, its strongly encouraged.
__str__()是一個Python 魔術的方法，它定義了什麼東西将会被返回假如你调用这个对象的str()。Django 使用str(obj)(或是相對應的函數，unicode(obj)，簡短地描述)，在很多地方，最有名，是這秀出來的值被這個物件重繪在Django 管理站，而且被寫入樣板的值，當它展示一個物件。因此，你必須總是返回一個好的，人類可讀的字串，對這個物件__str__。即使這不是必須的，它還是強列地被鼓勵 。
Heres an example:
這裏是一個範例:
class Person(models.Model):
first_name = models.CharField(maxlength=50)
last_name = models.CharField(maxlength=50)
def __str__(self):
return '%s %s' % (self.first_name, self.last_name)
Define a get_absolute_url() method to tell Django how to calculate the URL for an object, for example:
可以通过定义 get_absolute_url() 方法来告诉Django怎样得到一个对象的URL，例如：
def get_absolute_url(self):
return "/people/%i/" % self.id
Django uses this in its admin interface. If an object defines get_absolute_url() , the object-editing page will have a View on site link that will take you directly to the objects public view, according to get_absolute_url() .
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Also, a couple of other bits of Django, such as the syndication-feed framework, use get_absolute_url() as a convenience to reward people whove defined the method.
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Its good practice to use get_absolute_url() in templates, instead of hard-coding your objects URLs. For example, this template code is bad:
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<a href="/people/{{ object.id }}/">{{ object.name }}</a>
But this template code is good:
但这段模板代码就很优雅：
<a href="{{ object.get_absolute_url }}">{{ object.name }}</a>
The problem with the way we just wrote get_absolute_url() is that it slightly violates the DRY principle: the URL for this object is defined both in the URLconf file and in the model.
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You can further decouple your models from the URLconf using the permalink decorator. This decorator is passed the view function, a list of positional parameters, and (optionally) a dictionary of named parameters. Django then works out the correct full URL path using the URLconf, substituting the parameters you have given into the URL. For example, if your URLconf contained a line such as the following:
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(r'^people/(\d+)/$', 'people.views.details'),
your model could have a get_absolute_url method that looked like this:
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@models.permalink
def get_absolute_url(self):
return ('people.views.details', [str(self.id)])
Similarly, if you had a URLconf entry that looked like this:
与此类似，如果有这样的一个URLconf：
(r'/archive/(?P<year>\d{4})/(?P<month>\d{1,2})/(?P<day>\d{1,2})/$', archive_view)
you could reference this using permalink() as follows:
你可以像下面那样用permalink()来引用这个链接：
@models.permalink
def get_absolute_url(self):
return ('archive_view', (), {
'year': self.created.year,
'month': self.created.month,
'day': self.created.day})
Notice that we specify an empty sequence for the second argument in this case, because we want to pass only keyword arguments, not named arguments.
注意，我們指出一個空的序列，在這種案例的第二個參數，因為我們想要傳入只有關鍵字的參數，不是已命名的參數。
In this way, youre tying the models absolute URL to the view that is used to display it, without repeating the URL information anywhere. You can still use the get_absolute_url method in templates, as before.
用這個方法，你可以試著用模型的絕對URL ，指向view ，被用來展示它， 而不要在任何地方重覆URL 訊息。你仍然可以使用get_absolute_url方法，在樣板裏，就像之前一樣
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Feel free to write custom SQL statements in custom model methods and module-level methods. The object django.db.connection represents the current database connection. To use it, call connection.cursor() to get a cursor object. Then, call cursor.execute(sql, [params]) to execute the SQL, and cursor.fetchone() or cursor.fetchall() to return the resulting rows:
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def my_custom_sql(self):
from django.db import connection
cursor = connection.cursor()
cursor.execute("SELECT foo FROM bar WHERE baz = %s", [self.baz])
row = cursor.fetchone()
return row
connection and cursor mostly implement the standard Python DB-API (http://www.python.org/peps/pep-0249.html). If youre not familiar with the Python DB-API, note that the SQL statement in cursor.execute() uses placeholders, "%s" , rather than adding parameters directly within the SQL. If you use this technique, the underlying database library will automatically add quotes and escaping to your parameter(s) as necessary. (Also note that Django expects the "%s" placeholder, not the "?" placeholder, which is used by the SQLite Python bindings. This is for the sake of consistency and sanity.)
connection and cursor最常被實作，在標準的 Python DB-API (http://www.python.org/peps/pep-0249.html).假如你還不夠熟悉Python DB-API，注意在cursor.execute()SQL 句子。使用placeholders，%s，甚於直接在SQL裏加參數。假如你使用這個技巧，底下的資料庫函式庫將自動的加上引號給你的參數，視需要而定。(也注意Django 期待%splaceholder而不是?placeholder，後者用於SQLite Python連接。這是為了穩定性的考量。
A final note: If all you want to do is use a custom WHERE clause, you can just use the where , tables , and params arguments to the standard lookup API. See Appendix C.
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As explained in Appendix C, each model gets a few methods automatically most notably, save() and delete() . You can override these methods to alter behavior.
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A classic use-case for overriding the built-in methods is if you want something to happen whenever you save an object, for example:
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class Blog(models.Model):
name = models.CharField(maxlength=100)
tagline = models.TextField()
def save(self):
do_something()
super(Blog, self).save() # Call the "real" save() method.
do_something_else()
You can also prevent saving:
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class Blog(models.Model):
name = models.CharField(maxlength=100)
tagline = models.TextField()
def save(self):
if self.name == "Yoko Ono's blog":
return # Yoko shall never have her own blog!
else:
super(Blog, self).save() # Call the "real" save() method
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The Admin class tells Django how to display the model in the admin site.
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The following sections present a list of all possible Admin options. None of these options is required. To use an admin interface without specifying any options, use pass , like so:
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class Admin:
pass
Adding class Admin to a model is completely optional.
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Set date_hierarchy to the name of a DateField or DateTimeField in your model, and the change list page will include a date-based navigation using that field.
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Heres an example:
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class CustomerOrder(models.Model):
order_date = models.DateTimeField()
...
class Admin:
date_hierarchy = "order_date"
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Set fields to control the layout of admin interface add and change pages.
設定fields來控制管理畫面的輸出，加上，修改頁面
fields is a pretty complex nested data structure best demonstrated with an example. The following is taken from the FlatPage model thats part of django.contrib.flatpages :
欄位，是一個非常複雜巢狀的資料結構 ，可以很好的被一個範例展示。以下是擷取自FlatPage模型，這是django.contrib.flatpages的一部分
class FlatPage(models.Model):
...
class Admin:
fields = (
(None, {
'fields': ('url', 'title', 'content', 'sites')
}),
('Advanced options', {
'classes': 'collapse',
'fields' : ('enable_comments', 'registration_required', 'template_name')
}),
)
Formally, fields is a list of two tuples, in which each two-tuple represents a <fieldset> on the admin form page. (A <fieldset> is a section of the form.)
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The two-tuples are in the format (name, field_options) , where name is a string representing the title of the fieldset and field_options is a dictionary of information about the fieldset, including a list of fields to be displayed in it.
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If fields isnt given, Django will default to displaying each field that isnt an AutoField and has editable=True , in a single fieldset, in the same order as the fields are defined in the model.
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The field_options dictionary can have the keys described in the sections that follow.
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A tuple of field names to display in this fieldset. This key is required.
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To display multiple fields on the same line, wrap those fields in their own tuple. In this example, the first_name and last_name fields will display on the same line:
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'fields': (('first_name', 'last_name'), 'address', 'city', 'state'),
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A string containing extra CSS classes to apply to the fieldset.
一个包含要在fieldset上使用的CSS classes的字符串
Apply multiple classes by separating them with spaces:
通过空格分开已使用多个类：
'classes': 'wide extrapretty',
Two useful classes defined by the default admin site stylesheet are collapse and wide . Fieldsets with the collapse style will be initially collapsed in the admin site and replaced with a small click to expand link. Fieldsets with the wide style will be given extra horizontal space.
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A string of optional extra text to be displayed at the top of each fieldset, under the heading of the fieldset. Its used verbatim, so you can use any HTML and you must escape any special HTML characters (such as ampersands) yourself.
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A list of strings representing URLs of JavaScript files to link into the admin screen via <script src=""> tags. This can be used to tweak a given type of admin page in JavaScript or to provide quick links to fill in default values for certain fields.
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If you use relative URLs that is, URLs that dont start with http:// or / then the admin site will automatically prefix these links with settings.ADMIN_MEDIA_PREFIX .
Set list_display to control which fields are displayed on the change list page of the admin.
If you dont set list_display , the admin site will display a single column that displays the __str__() representation of each object.
Here are a few special cases to note about list_display :
这里是一些专门关于``list_display``的例子：
If the field is a ForeignKey , Django will display the __str__() of the related object.
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ManyToManyField fields arent supported, because that would entail executing a separate SQL statement for each row in the table. If you want to do this nonetheless, give your model a custom method, and add that methods name to list_display . (More information on custom methods in list_display shortly.)
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If the field is a BooleanField or NullBooleanField , Django will display a pretty on or off icon instead of True or False .
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If the string given is a method of the model, Django will call it and display the output. This method should have a short_description function attribute, for use as the header for the field.
Heres a full example model:
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class Person(models.Model):
name = models.CharField(maxlength=50)
birthday = models.DateField()
class Admin:
list_display = ('name', 'decade_born_in')
def decade_born_in(self):
return self.birthday.strftime('%Y')[:3] + "0's"
decade_born_in.short_description = 'Birth decade'
If the string given is a method of the model, Django will HTML-escape the output by default. If youd rather not escape the output of the method, give the method an allow_tags attribute whose value is True .
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Heres a full example model:
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class Person(models.Model):
first_name = models.CharField(maxlength=50)
last_name = models.CharField(maxlength=50)
color_code = models.CharField(maxlength=6)
class Admin:
list_display = ('first_name', 'last_name', 'colored_name')
def colored_name(self):
return '<span style="color: #%s;">%s %s</span>' % (self.color_code, self.first_name, self.last_name)
colored_name.allow_tags = True
If the string given is a method of the model that returns True or False , Django will display a pretty on or off icon if you give the method a boolean attribute whose value is True .
Heres a full example model:
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class Person(models.Model):
first_name = models.CharField(maxlength=50)
birthday = models.DateField()
class Admin:
list_display = ('name', 'born_in_fifties')
def born_in_fifties(self):
return self.birthday.strftime('%Y')[:3] == 5
born_in_fifties.boolean = True
The __str__() methods are just as valid in list_display as any other model method, so its perfectly OK to do this:
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list_display = ('__str__', 'some_other_field')
Usually, elements of list_display that arent actual database fields cant be used in sorting (because Django does all the sorting at the database level).
However, if an element of list_display represents a certain database field, you can indicate this fact by setting the admin_order_field attribute of the item, for example:
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class Person(models.Model):
first_name = models.CharField(maxlength=50)
color_code = models.CharField(maxlength=6)
class Admin:
list_display = ('first_name', 'colored_first_name')
def colored_first_name(self):
return '<span style="color: #%s;">%s</span>' % (self.color_code, self.first_name)
colored_first_name.allow_tags = True
colored_first_name.admin_order_field = 'first_name'
The preceding code will tell Django to order by the first_name field when trying to sort by colored_first_name in the admin site.
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Set list_display_links to control which fields in list_display should be linked to the change page for an object.
By default, the change list page will link the first column the first field specified in list_display to the change page for each item. But list_display_links lets you change which columns are linked. Set list_display_links to a list or tuple of field names (in the same format as list_display ) to link.
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list_display_links can specify one or many field names. As long as the field names appear in list_display , Django doesnt care how many (or how few) fields are linked. The only requirement is that if you want to use list_display_links , you must define list_display .
In this example, the first_name and last_name fields will be linked on the change list page:
在这个例子中，“first_name”和“last_name”将被链接到更改列表页
class Person(models.Model):
...
class Admin:
list_display = ('first_name', 'last_name', 'birthday')
list_display_links = ('first_name', 'last_name')
Finally, note that in order to use list_display_links , you must define list_display , too.
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Set list_filter to activate filters in the right sidebar of the change list page of the admin interface. This should be a list of field names, and each specified field should be either a BooleanField , DateField , DateTimeField , or ForeignKey .
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This example, taken from the django.contrib.auth.models.User model, shows how both list_display and list_filter work:
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class User(models.Model):
...
class Admin:
list_display = ('username', 'email', 'first_name', 'last_name', 'is_staff')
list_filter = ('is_staff', 'is_superuser')
Set list_per_page to control how many items appear on each paginated admin change list page. By default, this is set to 100 .
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Set ordering to specify how objects on the admin change list page should be ordered. This should be a list or tuple in the same format as a models ordering parameter.
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If this isnt provided, the Django admin interface will use the models default ordering.
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Set save_as to True to enable a save as feature on admin change forms.
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Normally, objects have three save options: Save, Save and continue editing, and Save and add another. If save_as is True , Save and add another will be replaced by a Save as button.
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Save as means the object will be saved as a new object (with a new ID), rather than the old object.
By default, save_as is set to False .
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Set save_on_top to add save buttons across the top of your admin change forms.
设置 save_on_top 在管理变更表单的顶部添加保存按钮。
Normally, the save buttons appear only at the bottom of the forms. If you set save_on_top , the buttons will appear both on the top and the bottom.
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By default, save_on_top is set to False .
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Set search_fields to enable a search box on the admin change list page. This should be set to a list of field names that will be searched whenever somebody submits a search query in that text box.
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These fields should be some kind of text field, such as CharField or TextField . You can also perform a related lookup on a ForeignKey with the lookup API follow notation:
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class Employee(models.Model):
department = models.ForeignKey(Department)
...
class Admin:
search_fields = ['department__name']
When somebody does a search in the admin search box, Django splits the search query into words and returns all objects that contain each of the words, case insensitive, where each word must be in at least one of search_fields . For example, if search_fields is set to ['first_name', 'last_name'] and a user searches for john lennon , Django will do the equivalent of this SQL WHERE clause:
当某人在管理查询框执行一次搜索时，Django 把查询内容切分成单词，并且返回包含了每个单词的所有对象，它们大写写敏感，并且每个单词必须出现在 查询字段 (search_fields)中的一个。举个例子，如果查询字段被设置成 ['first_name', 'last_name'] ，一个用户查找 john lennon ，Django 会执行和SQL的 WHERE 语句相同的事情。
WHERE (first_name ILIKE '%john%' OR last_name ILIKE '%john%') AND (first_name ILIKE '%lennon%' OR last_name ILIKE '%lennon%')
For faster and/or more restrictive searches, prefix the field name with an operator, as shown in Table B-7.
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| Operator | Meaning |
|---|---|
| ^ | Matches the beginning of the field. For example, if search_fields is set to ['^first_name', '^last_name'] , and a user searches for john lennon , Django will do the equivalent of this SQL WHERE clause: WHERE (first_name ILIKE 'john%' OR last_name ILIKE 'john%') AND (first_name ILIKE 'lennon%' OR last_name ILIKE 'lennon%') This query is more efficient than the normal '%john%' query, because the database only needs to check the beginning of a columns data, rather than seeking through the entire columns data. Plus, if the column has an index on it, some databases may be able to use the index for this query, even though its a LIKE query. |
| = | Matches exactly, case-insensitive. For example, if search_fields is set to ['=first_name', '=last_name'] and a user searches for john lennon , Django will do the equivalent of this SQL WHERE clause: WHERE (first_name ILIKE 'john' OR last_name ILIKE 'john') AND (first_name ILIKE 'lennon' OR last_name ILIKE 'lennon') Note that the query input is split by spaces, so, following this example, its currently not possible to search for all records in which first_name is exactly 'john winston' (containing a space). |
| @ | Performs a full-text match. This is like the default search method, but it uses an index. Currently this is available only for MySQL. |
| 操作符 | 含义 |
|---|---|
| ^ | 匹配字段的开头。例如，把 search_fields 设置成 ['^first_name', '^last_name'] ，当用户搜索 john lennon 时，Django相当于执行了这样的SQL WHERE 语句： WHERE (first_name ILIKE 'john%' OR last_name ILIKE 'john%') AND (first_name ILIKE 'lennon%' OR last_name ILIKE 'lennon%') 这个查询要比执行普通的 '%john%' 查询效率高，因为数据库只需要检查每一列数据的开头，而不用把整 列数据都扫一遍。此外，如果有针对这一列的索引的话，某些数据库可能会在查询中使用索引，即使它是一个 LIKE 查询。 |
| = | 精确匹配，不区分大小写。例如，把 search_fields 设置成 ['=first_name', '=last_name'] ，当 用户搜索 john lennon 时，Django相当于执行了这样的SQL WHERE 语句： WHERE (first_name ILIKE 'john' OR last_name ILIKE 'john') AND (first_name ILIKE 'lennon' OR last_name ILIKE 'lennon') 记住，搜索输入是靠空格来分隔的，所以，在这个例子中还不可能找出 first_name 恰恰是 'john winston' （中间有空格）的所有记录。 |
| @ | 执行全文匹配。这个和默认的搜索方法类似，但是它使用索引。目前只在MySQL中可用。 |
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