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diff --git a/docs/api-guide/relations.md b/docs/api-guide/relations.md new file mode 100644 index 00000000..351b5e09 --- /dev/null +++ b/docs/api-guide/relations.md @@ -0,0 +1,139 @@ +<a class="github" href="relations.py"></a> + +# Serializer relations + +> Bad programmers worry about the code. +> Good programmers worry about data structures and their relationships. +> +> — [Linus Torvalds][cite] + + +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`. + +--- + +**Note:** The relational fields are declared in `relations.py`, but by convention you should import them using `from rest_framework import serializers` and refer to fields as `serializers.<FieldName>`. + +--- + +## 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 customize this behavior 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',) + +Then an example output format for a Bookmark instance would be: + + { + 'tags': [u'django', u'python'], + 'url': u'https://www.djangoproject.com/' + } + +## PrimaryKeyRelatedField +## ManyPrimaryKeyRelatedField + +`PrimaryKeyRelatedField` and `ManyPrimaryKeyRelatedField` will represent the target of the relationship using it's primary key. + +By default these fields are read-write, although you can change this behavior using the `read_only` flag. + +**Arguments**: + +* `queryset` - By default `ModelSerializer` classes will use the default queryset for the relationship. `Serializer` classes must either set a queryset explicitly, or set `read_only=True`. +* `null` - If set to `True`, the field will accept values of `None` or the empty-string for nullable relationships. + +## SlugRelatedField +## ManySlugRelatedField + +`SlugRelatedField` and `ManySlugRelatedField` will represent the target of the relationship using a unique slug. + +By default these fields read-write, although you can change this behavior using the `read_only` flag. + +**Arguments**: + +* `slug_field` - The field on the target that should be used to represent it. This should be a field that uniquely identifies any given instance. For example, `username`. +* `queryset` - By default `ModelSerializer` classes will use the default queryset for the relationship. `Serializer` classes must either set a queryset explicitly, or set `read_only=True`. +* `null` - If set to `True`, the field will accept values of `None` or the empty-string for nullable relationships. + +## HyperlinkedRelatedField +## ManyHyperlinkedRelatedField + +`HyperlinkedRelatedField` and `ManyHyperlinkedRelatedField` will represent the target of the relationship using a hyperlink. + +By default, `HyperlinkedRelatedField` is read-write, although you can change this behavior using the `read_only` flag. + +**Arguments**: + +* `view_name` - The view name that should be used as the target of the relationship. **required**. +* `format` - If using format suffixes, hyperlinked fields will use the same format suffix for the target unless overridden by using the `format` argument. +* `queryset` - By default `ModelSerializer` classes will use the default queryset for the relationship. `Serializer` classes must either set a queryset explicitly, or set `read_only=True`. +* `slug_field` - The field on the target that should be used for the lookup. Default is `'slug'`. +* `pk_url_kwarg` - The named url parameter for the pk field lookup. Default is `pk`. +* `slug_url_kwarg` - The named url parameter for the slug field lookup. Default is to use the same value as given for `slug_field`. +* `null` - If set to `True`, the field will accept values of `None` or the empty-string for nullable relationships. + +## HyperLinkedIdentityField + +This field can be applied as an identity relationship, such as the `'url'` field on a HyperlinkedModelSerializer. + +This field is always read-only. + +**Arguments**: + +* `view_name` - The view name that should be used as the target of the relationship. **required**. +* `format` - If using format suffixes, hyperlinked fields will use the same format suffix for the target unless overridden by using the `format` argument. +* `slug_field` - The field on the target that should be used for the lookup. Default is `'slug'`. +* `pk_url_kwarg` - The named url parameter for the pk field lookup. Default is `pk`. +* `slug_url_kwarg` - The named url parameter for the slug field lookup. Default is to use the same value as given for `slug_field`. + +[cite]: http://lwn.net/Articles/193245/ |