=============== Model reference =============== Django's models are the bread and butter of the framework. There's a huge array of options available to you when defining your data models; this document explains all of them. Options for models ================== A list of all possible options for a model object follows. Although there's a wide array of possible options, only ``fields`` is required. ``admin`` A ``meta.Admin`` object; see `Admin options`_. If this field isn't given, the object will not have an admin interface. ``db_table`` The name of the database table to use for the module:: db_table = "pizza_orders" If not given, this will use ``app_label + '_' + module_name``. ``exceptions`` Names of extra exception subclasses to include in the generated module. These exceptions are available from instance methods and from module-level methods:: exceptions = ("DisgustingToppingsException", "BurntCrust") ``fields`` A list of field objects; see `Field objects`_. For example:: fields = ( meta.CharField('customer_name', 'customer name', maxlength=15), meta.BooleanField('use_extra_cheese', 'use extra cheese'), meta.IntegerField('customer_type', 'customer type', choices=CUSTOMER_TYPE_CHOICES), ... ) ``get_latest_by`` The name of a date or datetime field; if given, the module will have a ``get_latest()`` function which fetches the "latest" object in terms of that field:: get_latest_by = "order_date" ``module_constants`` A dict of name/values to use as extra module-level constants:: module_constants = { 'MEAT_TYPE_PEPPERONI' : 1, 'MEAT_TYPE_SAUSAGE' : 2, } ``module_name`` The name of the module:: module_name = "pizza_orders" If not given this will use a lowercased version of the class name. ``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:: order_with_respect_to = 'pizza_id' to allow the toppings to be ordered with respect to the associated pizza. ``ordering`` The default ordering for tho object:: ordering = (('order_date', 'DESC'),) This is a tuple of 2-tuples; each 2-tuple is ``(field_name, ordering_type)`` where ordering_type is either ``"ASC"`` or ``"DESC"``. You may also use the magic ``(None, "RANDOM")`` ordering tuple for random ordering. ``permissions`` Extra permissions to enter into the permissions table when creating this object. A add, delete, and change permission is automatically created for each object; this option specifies extra permissions:: permissions = (("may_delivier_pizzas", "Can deliver pizzas"),) This is a list of 2-tuples of ``(permission_code, human_readable_permission_name)``. ``unique_together`` Sets of field names that, taken together, must be unique:: unique_together = (("driver_id", "restaurant_id"),) This is a list of lists of fields that must be unique when considered together. ``verbose_name`` A human-readable name for the object, singular:: verbose_name = "pizza" If not given, this will use a munged version of the class name: ``CamelCase`` becomes ``camel case``. ``verbose_name_plural`` The plural name for the object:: verbose_name_plural = "stories" If not given, ``verbose_name + "s"`` will automatically be used. Field objects ============= The list of fields is the most important part of a data model. Each item in the ``fields`` list is an instance of a ``meta.Field`` subclass, and maps to a database field. All field objects -- except for ``ForeignKey`` and ``ManyToManyField`` (see below) -- take two positional arguments and a number of keyword arguments. The positional arguments are the field name and the human-readable name. The field name must be a valid Python identifier, but the human-readable name can contain spaces, punctuation, etc. General field options --------------------- Each type of field takes a different set of options, but there are some options that are common to all field types. These options are: ====================== =================================================== Option Description ====================== =================================================== ``blank`` If ``True``, the field is allowed to be blank. Note that this is different from ``null`` in that string fields will store the empty string instead of ``NULL`` internally; this means that to create a field that stores nulls you must pass ``blank=True`` and ``null=True`` . ``choices`` A list of 2-tuples to use as choices for this field.If this is given, instead of the standard field a option menu will be used, limiting choices to the choices given. A choices list looks like:: 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. ``core`` For objects that are edited inline to a related object (see Relationships_). If all "core" fields in an inline-edited object are cleared, the object will be considered to be deleted. It is an error to have an inline-editable relation without at least one core field. ``db_index`` If ``True``, the SQL generator will create a database index on this field. ``default`` The default value for the field. ``editable`` ``True`` by default, if set to ``False`` the field will not be editable in the admin. ``help_text`` Extra "help" text to be displayed with the field. ``null`` If ``True`` empty values in the field will be stored as ``NULL`` in the database. XXX does null imply blank? XXX ``primary_key`` If ``True`` this field is the primary key for the table. You only need to use this if you don't want the standard "id" field created and used as the primary key. Implies ``blank=False``, ``null=False``, and ``unique=True``. Only one primary key is allowed on each object. ``radio_admin`` If ``choices`` is given, or if the field is a ManyToOne relation, use a radio button interface for the choices instead of the standard options menu interface. ``rel`` The field's relation; see Relationships_. ``unique`` If ``True`` this field must be unique throughout the table. ``unique_for_date`` Set this to the name of a ``DateField`` or ``DateTimeField`` to require that this field be unique for the value of the date field. That is, if you have a field, ``title`` that has ``unique_for_date="pub_date"``, then it is an error to have two rows with the same ``title`` and the same ``pub_date``. ``unique_for_month`` Like ``unique_for_date``, but requires the field to be unique with respect to the month. ``unique_for_year`` Like ``unique_for_date`` and ``unique_for_month`` but, well, you get the idea. ``validator_list`` A list of extra validators to apply to the field. See the `Form fields guide`_ for information about validators. ====================== =================================================== .. _`Form fields guide`: http://www.djangoproject.com/FIXME/ Field Types ----------- ``AutoField`` An ``IntegerField`` that automatically increments. You usually won't need to use this directly; a primary key field will automatically be added to your model if you don't specify otherwise. That automatically added field is:: meta.AutoField('id', 'ID', primary_key=True) ``BooleanField`` A true/false field. ``CharField`` A text field. These are displayed in the admin as single-line text inputs, so for large amounts of text use a ``TextField``. ``CharField``s have an extra required argument: ``maxlength``; the maximum length (in characters) of the field. ``CommaSeparatedIntegerField`` A field of integers separated by commas. ``DateField`` A, um, date field. Has a few extra optional options: ====================== =================================================== Option Description ====================== =================================================== ``auto_now`` Automatically set the field to now every time the object is saved. Useful for "last-modified" timestamps. ``auto_now_add`` Automatically set the field to now when the object is first created. Useful for creation timestamps. ====================== =================================================== ``DateTimeField`` A date and time field. Takes the same extra options as ``DateField``. ``EmailField`` A ``CharField`` that checks that the value is a valid email address. Because validating email addresses can be tricky, this is a pretty loose test. ``FileField`` A file-upload field. Takes on additional option, ``upload_to`` which is a path to upload the file to. This path may contain `strftime formatting`_ which will be replaced by the date/time of the file upload (so that uploaded files don't fill up the given directory). .. _`strftime formatting`: http://docs.python.org/lib/module-time.html#l2h-1941 ``FloatField`` A floating-point number. Has two additional required options: ====================== =================================================== Option Description ====================== =================================================== ``max_digits`` The maximum number of digits allowed in the number. ``decimal_places`` The number of decimal places to store with the number ====================== =================================================== For example, to store numbers up to 999 with a resolution of 2 decimal places, you'd use:: meta.FloatField(..., max_digits=5, decimal_places=2) And to store numbers up to one million with a resolution of 10 decimal places:: meta.FloatField(..., max_digits=19, decimal_places=10) ``ForeignKey`` A many-to-one relationship to the primary key in another object. So, to give a ``Topping`` object a many-to-one relationship to ``Pizza`` (i.e. there are many toppings on a pizza):: meta.ForeignKey(Pizza) ``ForeignKey`` fields take a large number of options for defining how the relationship should work: ====================== =================================================== Option Description ====================== =================================================== ``edit_inline`` If ``True``, this related object is edited "inline" on the related object's page. This means that the object will not have its own admin interface. ``edit_inline_type`` This is either ``meta.TABULAR`` or ``meta.STACKED`` and controls weather the inline editable objects are displayed as a table or as a "stack" of fieldsets. Defaults to ``meta.STACKED``. ``limit_choices_to`` A dictionary of lookup arguments and values (see the `Database API reference`_) to limit choices of this object to. Use this along with ``meta.LazyDate`` to limit choices of objects by date, for example:: limit_choices_to = {'pub_date__lte' : meta.LazyDate()} only allows the choice of related objects with a ``pub_date`` before the current date/time to be chosen. 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. Thus, if a pizza could only have up to 10 toppings, ``max_num_in_admin=10`` would ensure that a user never enters more than 10 toppings. Note that this doesn't ensure more than 10 related toppings ever get created. ``min_num_in_admin`` The minimum number of related objects displayed in the admin. Normally, at the creation stage ``num_in_admin`` inline objects are shown, and at the edit stage ``num_extra_on_change`` 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 menu practical. Not used with ``edit_inline``. ``rel_name`` The name of the relation. In the above exmaple, this would default to 'pizza' (so that the ``Toppings`` object would have a ``get_pizza()`` function; if you set ``rel_name`` to "pie", then the function would be called ``get_pie()`` and the field name would be ``pie_id``. ``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:: meta.ForeignKey(Pizza) the ``related_name`` will be "topping" (taken from the class name which will in turn give ``Pizza`` methods like ``get_topping_list()`` and ``get_topping_count()``. If you instead were to use:: meta.ForeignKey(Pizza, related_name="munchie") then the methods would be called ``get_munchie_list()``, ``get_munchie_count()``, etc. 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:: ... meta.ForeignKey(Category, name="primary_category_id", rel_name="primary_category", related_name="primary_story"), meta.ForeignKey(Category, name="secondary_category_id", rel_name="secondary_category", related_name="secondary_story"), ... which would give the category objects methods named ``get_primary_story_list()`` and ``get_secondary_story_list()``. ``to_field`` The field on the related object that the relation is to. This is almost always ``id``, but if the PK on the other object is named something different, this is how to indicate that. ======================= ================================================== .. _`Database API reference`: http://www.djangoproject.com/documentation/db_api/ ``ImageField`` Like a ``FieldField``, but validates that the uploaded object is a valid image. Has two extra optional arguments, ``height_field`` and ``width_field`` which, if set, will be auto-populated with the height and width of the image. ``IntegerField`` An integer, surprisingly. ``IPAddressField`` An IP address, in string format (i.e. "24.124.1.30"). ``ManyToManyField`` XXX document once Adrian reworks this XXX ``NullBooleanField`` Like a ``BooleanField``, but allows ``NULL`` as one of the options. Use this instead of a ``BooleanField`` with ``null=True`` . ``PhoneNumberField`` Validates that the value is a valid phone number. ``PositiveIntegerField`` Like an ``IntegerField``, but must be positive. ``PositiveSmallIntegerField`` Like a ``PositiveIntegerField``, but only allows values below 32767. ``SlugField`` A "slug" suitable for parts of a URL; only allows alpha-numeric characters and underscores. Implies ``maxlength=50`` and ``db_index=True``. Accepts an extra option, ``prepopulate_from`` which is a list of fields from which to auto-populate the slug. ``SmallIntegerField`` Like an ``IntegerField``, but must be between -32768 and 32767. ``TextField`` A large text field (``