<a class="github" href="fields.py"></a>
# Serializer fields
> Flat is better than nested.
>
> — [The Zen of Python][cite]
Serializer fields handle converting between primative values and internal datatypes. They also deal with validating input values, as well as retrieving and setting the values from their parent objects.
---
**Note:** The serializer fields are declared in fields.py, but by convention you should import them using `from rest_framework import serializers` and refer to fields as `serializers.<FieldName>`.
---
# Generic Fields
These generic fields are used for representing arbitrary model fields or the output of model methods.
## Field
A generic, **read-only** field. You can use this field for any attribute that does not need to support write operations.
For example, using the following model.
class Account(models.Model):
owner = models.ForeignKey('auth.user')
name = models.CharField(max_length=100)
created = models.DateTimeField(auto_now_add=True)
payment_expiry = models.DateTimeField()
def has_expired(self):
now = datetime.datetime.now()
return now > self.payment_expiry
A serializer definition that looked like this:
class AccountSerializer(serializers.HyperlinkedModelSerializer):
expired = Field(source='has_expired')
class Meta:
fields = ('url', 'owner', 'name', 'expired')
Would produced output similar to:
{
'url': 'http://example.com/api/accounts/3/',
'owner': 'http://example.com/api/users/12/',
'name': 'FooCorp business account',
'expired': True
}
Be default, the `Field` class will perform a basic translation of the source value into primative datatypes, falling back to unicode representations of complex datatypes when neccesary.
You can customize this behaviour by overriding the `.to_native(self, value)` method.
## WritableField
A field that supports both read and write operations. By itself `WriteableField` does not perform any translation of input values into a given type. You won't typically use this field directly, but you may want to override it and implement the `.to_native(self, value)` and `.from_native(self, value)` methods.
## ModelField
A generic field that can be tied to any arbitrary model field. The `ModelField` class delegates the task of serialization/deserialization to it's associated model field. This field can be used to create serializer fields for custom model fields, without having to create a new custom serializer field.
**Signature:** `ModelField(model_field=<Django ModelField class>)`
---
# Typed Fields
These fields represent basic datatypes, and support both reading and writing values.
## BooleanField
A Boolean representation, corresponds to `django.db.models.fields.BooleanField`.
## CharField
A text representation, optionally validates the text to be shorter than `max_length` and longer than `min_length`, corresponds to `django.db.models.fields.CharField`
or `django.db.models.fields.TextField`.
**Signature:** `CharField([max_length=<Integer>[, min_length=<Integer>]])`
## EmailField
A text representation, validates the text to be a valid e-mail adress. Corresponds to `django.db.models.fields.EmailField`
## DateField
A date representation. Corresponds to `django.db.models.fields.DateField`
## DateTimeField
A date and time representation. Corresponds to `django.db.models.fields.DateTimeField`
## IntegerField
An integer representation. Corresponds to `django.db.models.fields.IntegerField`, `django.db.models.fields.SmallIntegerField`, `django.db.models.fields.PositiveIntegerField` and `django.db.models.fields.PositiveSmallIntegerField`
## FloatField
A floating point representation. Corresponds to `django.db.models.fields.FloatField`.
---
# Relational Fields
Relational fields are used to represent model relationships. They can be applied to `ForeignKey`, `ManyToManyField` and `OneToOneField` relationships, as well as to reverse relationships, and custom relationships such as `GenericForeignKey`.
## RelatedField
This field can be applied to any of the following:
* A `ForeignKey` field.
* A `OneToOneField` field.
* A reverse OneToOne relationship
* Any other "to-one" relationship.
By default `RelatedField` will represent the target of the field using it's `__unicode__` method.
You can customise this behaviour by subclassing `ManyRelatedField`, and overriding the `.to_native(self, value)` method.
## ManyRelatedField
This field can be applied to any of the following:
* A `ManyToManyField` field.
* A reverse ManyToMany relationship.
* A reverse ForeignKey relationship
* Any other "to-many" relationship.
By default `ManyRelatedField` will represent the targets of the field using their `__unicode__` method.
For example, given the following models:
class TaggedItem(models.Model):
"""
Tags arbitrary model instances using a generic relation.
See: https://docs.djangoproject.com/en/dev/ref/contrib/contenttypes/
"""
tag = models.SlugField()
content_type = models.ForeignKey(ContentType)
object_id = models.PositiveIntegerField()
content_object = GenericForeignKey('content_type', 'object_id')
def __unicode__(self):
return self.tag
class Bookmark(models.Model):
"""
A bookmark consists of a URL, and 0 or more descriptive tags.
"""
url = models.URLField()
tags = GenericRelation(TaggedItem)
And a model serializer defined like this:
class BookmarkSerializer(serializers.ModelSerializer):
tags = serializers.ManyRelatedField(source='tags')
class Meta:
model = Bookmark
exclude = ('id',)
The an example output format for a Bookmark instance would be:
{
'tags': [u'django', u'python'],
'url': u'https://www.djangoproject.com/'
}
## PrimaryKeyRelatedField
As with `RelatedField` field can be applied to any "to-one" relationship, such as a `ForeignKey` field.
`PrimaryKeyRelatedField` will represent the target of the field using it's primary key.
Be default, `PrimaryKeyRelatedField` is read-write, although you can change this behaviour using the `readonly` flag.
## ManyPrimaryKeyRelatedField
As with `RelatedField` field can be applied to any "to-many" relationship, such as a `ManyToManyField` field, or a reverse `ForeignKey` relationship.
`PrimaryKeyRelatedField` will represent the target of the field using their primary key.
Be default, `ManyPrimaryKeyRelatedField` is read-write, although you can change this behaviour using the `readonly` flag.
## HyperlinkedRelatedField
## ManyHyperlinkedRelatedField
## HyperLinkedIdentityField
[cite]: http://www.python.org/dev/peps/pep-0020/