.. _ref-fields: =============== Resource Fields =============== When designing an API, an important component is defining the representation of the data you're presenting. Like Django models, you can control the representation of a ``Resource`` using fields. There are a variety of fields for various types of data. Quick Start =========== For the impatient:: import datetime from tastypie import fields from tastypie.resources import Resource from myapp.api.resources import ProfileResource, NoteResource class PersonResource(Resource): name = fields.CharField(attribute='name') age = fields.IntegerField(attribute='years_old', null=True) created = fields.DateTimeField(readonly=True, help_text='When the person was created', default=datetime.datetime.now) is_active = fields.BooleanField(default=True) profile = fields.ToOneField(ProfileResource, 'profile') notes = fields.ToManyField(NoteResource, 'notes', full=True) Standard Data Fields ==================== All standard data fields have a common base class ``ApiField`` which handles the basic implementation details. .. note:: You should not use the ``ApiField`` class directly. Please use one of the subclasses that is more correct for your data. Common Field Options -------------------- All ``ApiField`` objects accept the following options. ``attribute`` ~~~~~~~~~~~~~ .. attribute:: ApiField.attribute A string naming an instance attribute of the object wrapped by the Resource. The attribute will be accessed during the ``dehydrate`` or or written during the ``hydrate``. Defaults to ``None``, meaning data will be manually accessed. ``default`` ~~~~~~~~~~~ .. attribute:: ApiField.default Provides default data when the object being ``dehydrated``/``hydrated`` has no data on the field. Defaults to ``tastypie.fields.NOT_PROVIDED``. ``null`` ~~~~~~~~ .. attribute:: ApiField.null Indicates whether or not a ``None`` is allowable data on the field. Defaults to ``False``. ``blank`` ~~~~~~~~~ .. attribute:: ApiField.blank Indicates whether or not data may be omitted on the field. Defaults to ``False``. This is useful for allowing the user to omit data that you can populate based on the request, such as the ``user`` or ``site`` to associate a record with. ``readonly`` ~~~~~~~~~~~~ .. attribute:: ApiField.readonly Indicates whether the field is used during the ``hydrate`` or not. Defaults to ``False``. ``unique`` ~~~~~~~~~~ .. attribute:: ApiField.unique Indicates whether the field is a unique identifier for the object. ``help_text`` ~~~~~~~~~~~~~ .. attribute:: ApiField.help_text A human-readable description of the field exposed at the schema level. Defaults to the per-Field definition. Field Types ----------- .. module:: tastypie.fields ``BooleanField`` ---------------- A boolean field. Covers both ``models.BooleanField`` and ``models.NullBooleanField``. ``CharField`` ------------- A text field of arbitrary length. Covers both ``models.CharField`` and ``models.TextField``. ``DateField`` ------------- A date field. ``DateTimeField`` ----------------- A datetime field. ``DecimalField`` ---------------- A decimal field. ``DictField`` ------------- A dictionary field. ``FileField`` ------------- A file-related field. Covers both ``models.FileField`` and ``models.ImageField``. ``FloatField`` -------------- A floating point field. ``IntegerField`` ---------------- An integer field. Covers ``models.IntegerField``, ``models.PositiveIntegerField``, ``models.PositiveSmallIntegerField`` and ``models.SmallIntegerField``. ``ListField`` ------------- A list field. ``TimeField`` ------------- A time field. Relationship Fields =================== Provides access to data that is related within the database. The ``RelatedField`` base class is not intended for direct use but provides functionality that ``ToOneField`` and ``ToManyField`` build upon. The contents of this field actually point to another ``Resource``, rather than the related object. This allows the field to represent its data in different ways. The abstractions based around this are "leaky" in that, unlike the other fields provided by ``tastypie``, these fields don't handle arbitrary objects very well. The subclasses use Django's ORM layer to make things go, though there is no ORM-specific code at this level. Common Field Options -------------------- In addition to the common attributes for all `ApiField`, relationship fields accept the following. ``to`` ~~~~~~ .. attribute:: RelatedField.to The ``to`` argument should point to a ``Resource`` class, NOT to a ``Model``. Required. ``full`` ~~~~~~~~ .. attribute:: RelatedField.full Indicates how the related ``Resource`` will appear post-``dehydrate``. If ``False``, the related ``Resource`` will appear as a URL to the endpoint of that resource. If ``True``, the result of the sub-resource's ``dehydrate`` will be included in full. ``related_name`` ~~~~~~~~~~~~~~~~ .. attribute:: RelatedField.related_name Used to help automatically populate reverse relations when creating data. Defaults to ``None``. In order for this option to work correctly, there must be a field on the other ``Resource`` with this as an ``attribute/instance_name``. Usually this just means adding a reflecting ``ToOneField`` pointing back. Example:: class EntryResource(ModelResource): authors = fields.ToManyField('path.to.api.resources.AuthorResource', 'author_set', related_name='entry') class Meta: queryset = Entry.objects.all() resource_name = 'entry' class AuthorResource(ModelResource): entry = fields.ToOneField(EntryResource, 'entry') class Meta: queryset = Author.objects.all() resource_name = 'author' Field Types ----------- ``ToOneField`` ~~~~~~~~~~~~~~ Provides access to related data via foreign key. This subclass requires Django's ORM layer to work properly. ``OneToOneField`` ~~~~~~~~~~~~~~~~~ An alias to ``ToOneField`` for those who prefer to mirror ``django.db.models``. ``ForeignKey`` ~~~~~~~~~~~~~~ An alias to ``ToOneField`` for those who prefer to mirror ``django.db.models``. ``ToManyField`` ~~~~~~~~~~~~~~~ Provides access to related data via a join table. This subclass requires Django's ORM layer to work properly. This field also has special behavior when dealing with ``attribute`` in that it can take a callable. For instance, if you need to filter the reverse relation, you can do something like:: subjects = fields.ToManyField(SubjectResource, attribute=lambda bundle: Subject.objects.filter(notes=bundle.obj, name__startswith='Personal')) Note that the ``hydrate`` portions of this field are quite different than any other field. ``hydrate_m2m`` actually handles the data and relations. This is due to the way Django implements M2M relationships. ``ManyToManyField`` ~~~~~~~~~~~~~~~~~~~ An alias to ``ToManyField`` for those who prefer to mirror ``django.db.models``. ``OneToManyField`` ~~~~~~~~~~~~~~~~~~ An alias to ``ToManyField`` for those who prefer to mirror ``django.db.models``.