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Proofread some of docs/model-api.txt. Still not done with this one. 

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2829 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Adrian Holovaty 2006-05-04 04:59:45 +00:00
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docs/model-api.txt
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@ -37,7 +37,7 @@ This example model defines a ``Person``, which has a ``first_name`` and
``first_name`` and ``last_name`` are *fields* of the model. Each field is
specified as a class attribute, and each attribute maps to a database column.
The above ``Person`` model would create an SQL table like this::
The above ``Person`` model would create a database table like this::
CREATE TABLE myapp_person (
"id" serial NOT NULL PRIMARY KEY,
@ -45,7 +45,7 @@ The above ``Person`` model would create an SQL table like this::
"last_name" varchar(30) NOT NULL
);
Three technical notes:
Some technical notes:
* The name of the table, ``myapp_person``, is automatically derived from
some model metadata but can be overridden. See _`Table names` below.
@ -630,16 +630,16 @@ any other ``Field`` type: by including it as a class attribute of your model.
``ForeignKey`` requires a positional argument: The class to which the model is
related.
For example, if a ``Place`` model is in a ``City`` -- that is, a ``City``
contains multiple places but each ``Place`` is only in one ``City`` -- use the
following definitions::
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::
class City(models.Model):
class Manufacturer(models.Model):
# ...
class Place(models.Model):
class Car(models.Model):
manufacturer = models.ForeignKey(Manufacturer)
# ...
city = models.ForeignKey(City)
To create a recursive relationship -- an object that has a many-to-one
relationship with itself -- use ``models.ForeignKey('self')``.
@ -647,18 +647,30 @@ relationship with itself -- use ``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::
class Place(models.Model):
# ...
city = models.ForeignKey("City")
class City(models.Model):
class Car(models.Model):
manufacturer = models.ForeignKey('Manufacturer')
# ...
The name of a ``ForeignKey`` (``city`` in the example above) generally should
be the name of the model, in singular form. Behind the scenes, Django appends
"_id" to the field name to create its database column name. However, your code
class Manufacturer(models.Model):
# ...
Note, however, that support for strings around model names in ``ForeignKey`` is
quite new, and it can be buggy in some cases.
Behind the scenes, Django appends ``"_id"`` to the field name to create its
database column name. In the above example, the database table for the ``Car``
model will have a ``manufacturer_id`` column. (You can change this explicitly
by specifying ``db_column``; see ``db_column`` below.) However, your code
should never have to deal with the database column name, unless you write
custom SQL.
custom SQL. You'll always deal with the field names of your model object.
It's suggested, but not required, that the name of a ``ForeignKey`` field
(``manufacturer`` in the example above) be the name of the model, lowercase.
You can, of course, call the field whatever you want. For example::
class Car(models.Model):
company_that_makes_it = models.ForeignKey(Manufacturer)
# ...
See the `Many-to-one relationship model example`_ for a full example.
@ -684,7 +696,7 @@ relationship should work. All are optional:
with ``models.LazyDate`` to limit choices of objects
by date. For example::
limit_choices_to = {'pub_date__lte' : models.LazyDate()}
limit_choices_to = {'pub_date__lte': models.LazyDate()}
only allows the choice of related objects with a
``pub_date`` before the current date/time to be
@ -699,8 +711,9 @@ relationship should work. All are optional:
that a user never enters more than 10 toppings.
Note that this doesn't ensure more than 10 related
toppings ever get created. It just controls the
interface.
toppings ever get created. It simply controls the
admin interface; it doesn't enforce things at the
Python API level or database level.
``min_num_in_admin`` The minimum number of related objects displayed in
the admin. Normally, at the creation stage,
@ -725,35 +738,9 @@ relationship should work. All are optional:
Not used with ``edit_inline``.
``related_name`` The name to use for the relation from the related
object back to this one. For example, when if
``Topping`` has this field::
models.ForeignKey(Pizza)
the ``related_name`` will be "topping_set" (taken from
the class name), which will in turn give ``Pizza``
a ``topping_set`` Object Set Descriptor.
If you instead were to use::
models.ForeignKey(Pizza, related_name="munchies")
then the Object Set Descriptor on ``Topping`` would
be called ``munchies``.
This is only really useful when you have a single
object that relates to the same object more than
once. For example, if a ``Story`` object has both
``primary_category`` and ``secondary_category``
fields, to make sure that the ``Category`` objects
have the correct methods, you'd use fields like::
models.ForeignKey(Category, related_name="primary_stories")
models.ForeignKey(Category, related_name="secondary_stories")
...which would give ``Category`` objects two Object Set
descriptors - one called ``primary_stories`` and one
called ``secondary_stories``.
object back to this one. See the
`related objects documentation`_ for a full
explanation and example.
``to_field`` The field on the related object that the relation
is to. By default, Django uses the primary key of
@ -761,6 +748,7 @@ relationship should work. All are optional:
======================= ============================================================
.. _`Database API reference`: http://www.djangoproject.com/documentation/db_api/
.. _related objects documentation: http://www.djangoproject.com/documentation/db_api/#related-objects
Many-to-many relationships
~~~~~~~~~~~~~~~~~~~~~~~~~~
@ -784,11 +772,12 @@ here's how you'd represent that::
toppings = models.ManyToManyField(Topping)
As with ``ForeignKey``, a relationship to self can be defined by using the
string ``"self"`` instead of the model name; references to as-yet undefined
models can be made by using a string containing the model name.
string ``'self'`` instead of the model name, and you can refer to as-yet
undefined models by using a string containing the model name.
The name of a ``ManyToManyField`` (``toppings`` in the example above) should
generally be a plural describing the set of related model objects.
It's suggested, but not required, that the name of a ``ManyToManyField``
(``toppings`` in the example above) be a plural describing the set of related
model objects.
Behind the scenes, Django creates an intermediary join table to represent the
many-to-many relationship.
@ -797,11 +786,11 @@ It doesn't matter which model gets the ``ManyToManyField``, but you only need
it in one of the models -- not in both.
Generally, ``ManyToManyField`` instances should go in the object that's going
to be edited in the admin. In the above example, ``toppings`` is in ``Pizza``
(rather than ``Topping`` having a ``pizzas`` ``ManyToManyField`` ) because it's
more natural to think about a ``Pizza`` having toppings than a topping being on
multiple pizzas. The way it's set up above, the ``Pizza`` admin form would let
users select the toppings.
to be edited in the admin interface, if you're using Django's admin. In the
above example, ``toppings`` is in ``Pizza`` (rather than ``Topping`` having a
``pizzas`` ``ManyToManyField`` ) because it's more natural to think about a
``Pizza`` having toppings than a topping being on multiple pizzas. The way it's
set up above, the ``Pizza`` admin form would let users select the toppings.
See the `Many-to-many relationship model example`_ for a full example.
@ -813,8 +802,7 @@ the relationship should work. All are optional:
======================= ============================================================
Argument Description
======================= ============================================================
``related_name`` See the description of ``related_name`` in
``ForeignKey`` above.
``related_name`` See the description under ``ForeignKey`` above.
``filter_interface`` Use a nifty unobtrusive Javascript "filter" interface
instead of the usability-challenged ``<select multiple>``
@ -825,14 +813,6 @@ the relationship should work. All are optional:
``limit_choices_to`` See the description under ``ForeignKey`` above.
``singular`` The singular name of the field. Use to name the ``get_*``
methods: in the example above, Django gives the ``Pizza``
objects a ``get_topping_list()`` method, where ``topping``
is the default ``singular`` value derived from the lowercase
version of the class being linked to. Use the singular
parameter to change this, which is if you want one model to
have multiple ``ManyToMany`` relationships to another model.
``symmetrical`` Only used in the definition of ManyToManyFields on self.
Consider the following model:
@ -840,21 +820,26 @@ the relationship should work. All are optional:
friends = models.ManyToManyField("self")
When Django processes this model, it identifies that it has
a ManyToManyField on itself, and as a result, it doesn't 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.
a ``ManyToManyField`` on itself, and as a result, it
doesn't 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, allow
ManyToMany relationships to be non-symmetrical.
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
non-symmetrical.
======================= ============================================================
One-to-one relationships
~~~~~~~~~~~~~~~~~~~~~~~~
The semantics of one-to-one relationships will be changing soon, so we don't
recommend you use them. If that doesn't scare you away, keep reading.
To define a one-to-one relationship, use ``OneToOneField``. You use it just
like any other ``Field`` type: by including it as a class attribute of your
model.
@ -903,11 +888,12 @@ Here's a list of all possible ``Meta`` options. No options are required. Adding
``db_table``
------------
The name of the database table to use for the module::
The name of the database table to use for the model::
db_table = "pizza_orders"
db_table = 'music_album'
If this isn't given, Django will use ``app_label + '_' + model_class_name``.
See "Table names" below for more.
If your database table name is an SQL reserved word, or contains characters
that aren't allowed in Python variable names -- notably, the hyphen --
@ -916,27 +902,32 @@ that's OK. Django quotes column and table names behind the scenes.
``get_latest_by``
-----------------
The name of a ``DateField`` or ``DateTimeField``. If given, the module will
have a ``get_latest()`` function that fetches the "latest" object according
to that field::
The name of a ``DateField`` or ``DateTimeField`` in the model. This specifies
the default field to use in your model ``Manager``'s ``latest()`` method.
Example::
get_latest_by = "order_date"
See `Getting the "latest" object`_ for a full example.
See the `docs for latest()`_ for more.
.. _Getting the "latest" object: http://www.djangoproject.com/documentation/models/get_latest/
.. _docs for latest(): http://www.djangoproject.com/documentation/db_api/#latest-field-name-none
``order_with_respect_to``
-------------------------
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 a ``PizzaToppping`` relates to
a ``Pizza`` object, you might use::
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, you'd do this::
order_with_respect_to = 'pizza'
class Answer(models.Model):
question = models.ForeignKey(Question)
# ...
...to allow the toppings to be ordered with respect to the associated pizza.
class Meta:
order_with_respect_to = 'question'
``ordering``
------------
@ -1012,177 +1003,297 @@ The plural name for the object::
If this isn't given, Django will use ``verbose_name + "s"``.
========================================
THE REST OF THIS HAS NOT YET BEEN EDITED
========================================
Table names
===========
To save you time, Django automatically derives the name of the database table
from the name of your model class and the app that contains it. A model's
database table name is constructed by joining the model's "app label" -- the
name you used in ``manage.py startapp`` -- to the model's class name, with an
underscore between them.
For example, if you have an app ``bookstore`` (as created by
``manage.py startapp bookstore``), a model defined as ``class Book`` will have
a database table named ``bookstore_book``.
To override the database table name, use the ``db_table`` parameter in
``class Meta``.
Automatic primary key fields
============================
By default, Django gives each model the following field::
id = models.AutoField(primary_key=True)
This is an auto-incrementing primary key.
If you'd like to specify a custom primary key, just specify ``primary_key=True``
on one of your fields. If Django sees you've explicitly set ``primary_key``, it
won't add the automatic ``id`` column.
Each model requires exactly one field to have ``primary_key=True``.
Admin options
=============
If you want your model to be visible to the automatic Administration
system, your model must have an inner ``"class Admin"``, like so::
If you want your model to be visible to Django's admin site, give your model an
inner ``"class Admin"``, like so::
class Person(models.Model):
first_name = models.CharField(maxlength=30)
last_name = models.CharField(maxlength=30)
class Foo(models.Model):
bar = models.CharField(maxlength=30)
# ...
class Admin:
# ...
# Admin options go here
pass
The Admin class gives instructions to Django on how to display the Model
to the Administration system.
The ``Admin`` class tells Django how to display the model in the admin site.
Here's a list of all possible ``Admin`` options. No options are required. Adding
``class Admin`` to a model is completely optional.
Here's a list of all possible ``Admin`` options. None of these options are
required. To use an admin interface without specifying any options, use
``pass``, like so::
class Admin:
pass
Adding ``class Admin`` to a model is completely optional.
``date_hierarchy``
To allow filtering of objects in the admin by date, set ``date_hierarchy``
to the name of the field to filter by::
------------------
date_hierarchy = 'order_date'
Set ``date_hierarchy`` to the name of a ``DateField`` or ``DateTimeField`` in
your model, and the change list page will include a date-based drilldown
navigation by that field.
Example::
date_hierarchy = 'pub_date'
``fields``
A list of fieldsets to display on the admin page. Each fieldset is a 2-tuple:
``(name, field_options)``. The ``name`` is a string to name the field set,
and ``field_options`` is a dictionary of information about the fields to be
displayed in that fieldset. This dictionary has the following keys:
----------
``fields``
A tuple of field names to display in this fieldset. To display
multiple fields on the same line, wrap those fields in their
own tuple.
Set ``fields`` to control the layout of admin "add" and "change" pages.
This key is required in the dictionary.
``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.)
``classes``
Extra CSS classes to apply to the fieldset. This is a simple
string. You can apply multiple classes by separating them with
spaces.
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.
Two useful classes defined by the default stylesheet are
``collapse`` and ``wide``. Fieldsets with the ``collapse`` style
will be initially collapsed in the admin and replaced with a small
"click to expand" link. Fieldsets with the ``wide`` style will be
given extra horizontal space.
A full example, taken from the ``django.contrib.flatpages.FlatPage`` model::
``description``
Optional extra text to be displayed at the top of each fieldset,
underneath the heading of the fieldset. It is used verbatim,
so you can use any HTML and you must escape any special HTML
characters (such as ampersand) yourself.
class Admin:
fields = (
(None, {
'fields': ('url', 'title', 'content', 'sites')
}),
('Advanced options', {
'classes': 'collapse',
'fields' : ('enable_comments', 'registration_required', 'template_name')
}),
)
For example (taken from the ``django.contrib.flatpages`` model)::
This results in an admin page that looks like:
class Admin:
...
fields = (
(None, {
'fields': ('url', 'title', 'content', 'sites')
}),
('Advanced options', {
'classes': 'collapse',
'fields' : ('enable_comments', 'registration_required', 'template_name')
}),
)
.. image:: http://media.djangoproject.com/img/doc/flatfiles_admin.png
results in an admin that looks like:
If ``fields`` isn't given, Django will default to displaying each field that
isn't an ``AutoField`` and has ``editable=True``, in a single fieldset, in
the same order as the fields are defined in the model.
.. image:: http://media.djangoproject.com/img/doc/flatfiles_admin.png
The ``field_options`` dictionary can have the following keys::
If ``fields`` isn't given Django will default to displaying each field that
isn't an ``AutoField`` and has ``editable=True``, in a single fieldset, in
the same order as the fields are defined in the model.
``fields``
~~~~~~~~~~
A tuple of field names to display in this fieldset. This key is required.
Example::
{
'fields': ('first_name', 'last_name', 'address', 'city', 'state'),
}
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::
{
'fields': (('first_name', 'last_name'), 'address', 'city', 'state'),
}
``classes``
~~~~~~~~~~~
A string containing extra CSS classes to apply to the fieldset.
Example::
{
'classes': 'wide',
}
Apply multiple classes by separating them with spaces. Example::
{
'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 and replaced with a small "click to expand"
link. Fieldsets with the ``wide`` style will be given extra horizontal space.
``description``
~~~~~~~~~~~~~~~
A string of optional extra text to be displayed at the top of each fieldset,
under the heading of the fieldset. It's used verbatim, so you can use any HTML
and you must escape any special HTML characters (such as ampersands) yourself.
``js``
A list of strings representing URLs of JavaScript files to link into the
admin screen. This can be used to tweak a given type of admin page in JS or
to provide "quick links" to fill in default values for certain fields.
------
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.
``list_display``
List of fields to display on the list page in the admin.
----------------
There are a few special cases that do other things besides displaying the
contents of the given fields:
Set ``list_display`` to control which fields are displayed on the change list
page of the admin.
* If the field given is a ``ForeignKey``, the ``repr()`` of the related
object will be displayed.
Example::
* ``ManyToManyField`` fields aren't supported, because that would
entail executing a separate SQL statement for each row in the table.
list_display = ('first_name', 'last_name')
* If the field is a ``BooleanField``, a "on" or "off" icon will
be displayed instead of ``True`` or ``False``.
If you don't set ``list_display``, the admin site will display a single column
that displays the ``__str__()`` representation of each object.
* If the field name is a method of the model, it'll be called, and the
output will be displayed. This method should have a
``short_description`` function attribute, for use as the header for
the field.
A few special cases to note about ``list_display``:
* Use the string ``"__str__"`` to output the representation of the
object, according to your model's ``__str__()`` function. If you
don't define ``list_display``, Django will use the ``__str__`` by
default.
* If the field is a ``ForeignKey``, Django will display the ``__str__()``
of the related object.
See the example below.
* ``ManyToManyField`` fields aren't supported, because that would entail
executing a separate SQL statement for each row in the table.
* If the field is a ``BooleanField``, Django will display a pretty "on" or
"off" icon instead of ``True`` or ``False``.
* 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.
Here's a full example model::
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'
``list_filter``
List of fields to filter by. Each field should either be a ``BooleanField``
or else a field with a ``ManyToOne`` relation.
---------------
Here's an example of how ``list_display`` and ``list_filter`` work (taken
from the ``auth.user`` model)::
Set ``list_filter`` to activate filters in the right sidebar of the change list
page of the admin. This should be a list of field names, and each specified
field should be either a ``BooleanField``, ``DateField``, ``DateTimeField``
or ``ForeignKey``.
class Admin:
#...
list_display = ('username', 'email', 'first_name', 'last_name', 'is_staff')
list_filter = ('is_staff', 'is_superuser')
This example, taken from the ``django.contrib.auth.models.User`` model, shows
how both ``list_display`` and ``list_filter`` work::
The above code results in an admin that looks like this:
class Admin:
list_display = ('username', 'email', 'first_name', 'last_name', 'is_staff')
list_filter = ('is_staff', 'is_superuser')
.. image:: http://media.djangoproject.com/img/doc/users_changelist.png
The above code results in an admin change list page that looks like this:
(This example also has ``search_fields`` defined; see below).
.. image:: http://media.djangoproject.com/img/doc/users_changelist.png
(This example also has ``search_fields`` defined. See below.)
``list_select_related``
Either ``True`` or ``False``. Default is ``False``. If ``True``, the admin
change list page will use the ``select_related`` database-API parameter in
its query that retrieves the list of items.
-----------------------
Note that Django will use ``select_related``, regardless of this setting,
if one of the ``list_display`` fields is a ``ForeignKey``.
Set ``list_select_related`` to tell Django to use ``select_related()`` in
retrieving the list of objects on the admin change list page. This can save you
a bunch of database queries.
The value should be either ``True`` or ``False``. Default is ``False``.
Note that Django will use ``select_related()``, regardless of this setting,
if one of the ``list_display`` fields is a ``ForeignKey``.
For more on ``select_related()``, see `the select_related() docs`_.
.. _the select_related() docs: http://www.djangoproject.com/documentation/db_api/#select-related
``ordering``
A list or tuple (see the `Meta options`_, above) that gives a
different ordering for the admin change list. If this isn't given, the
model's default ordering will be used.
------------
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 model's
``ordering`` parameter.
If this isn't provided, the Django admin will use the model's default ordering.
``save_as``
Enables a "save as" feature on object pages. 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.
-----------
"Save as" means the object will be saved as a new object (with a new ID),
rather than the old object.
Set ``save_as`` to enable a "save as" feature on admin change forms.
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.
"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``.
``save_on_top``
If this option is ``True``, object pages will have the save buttons across
the top as well as at the bottom of the page.
---------------
Set ``save_on_top`` to add save buttons across the top of your admin change
forms.
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.
By default, ``save_on_top`` is set to ``False``.
``search_fields``
A list of field names to provide a text search for. These fields should,
obviously, be some kind of text field, such as ``CharField`` or
``TextField``.
-----------------
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.
These fields should be some kind of text field, such as ``CharField`` or
``TextField``.
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::
WHERE (first_name ILIKE '%john%' OR last_name ILIKE '%john%')
AND (first_name ILIKE '%lennon%' OR last_name ILIKE '%lennon%')
Managers
========
@ -1339,6 +1450,9 @@ method::
Manipulator methods
-------------------
(The functionality in this section is going away soon. This documentation is
provided only for legacy purposes at this point.)
Similarly, you can add methods to the object's manipulators by defining methods
that being with "_manipulator_". This is most useful for providing custom
validators for certain fields, because manipulators automatically call any