Serializer fields

Flat is better than nested.

— The Zen of Python

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.