field.py

class ReverseField(Field):
	"""
	Simple read only field for returning reverse URLs.

	This field utilizes information from the object being serialized. It does
	not care about what the current URL contains, lookup fields in the URL,
	nor the structure of a model. Instead, it takes the field names passed
	into lookup_fields and reads the values of those fields from the object.
	The values are then passed as arguments to the reverse function, which
	constructs the final URL.

	This field should be used instead of HyperlinkedRelatedField because it
	does not depend on URL keywords. It is not always possible to know which
	keyword arguments were used for finding the object. It may also be
	necessary to use more than a single keyword when constructing the URL.

	Reverse field currently does not support traversals past the current
	object. However, this functionality would not be difficult to add. See
	KeyFilterBackend for an example of how to traverse fields.
	"""

	def __init__(self, view_name, lookup_fields=('pk',), **kwargs):
		self.view_name = view_name
		self.lookup_fields = lookup_fields
		super(ReverseField, self).__init__(**kwargs)

	def field_to_native(self, obj, field_name):
		# There is no primary key if the object has not yet been saved.
		# Generating the URL becomes impossible if we need the key before
		# it is available. Thus, we resign to our fate and return None.
		if 'pk' in self.lookup_fields and getattr(obj, 'pk', None) is None:
			return None

		request = self.context.get('request', None)

		if request is None:
			raise KeyError("ReverseField requires the request object to be present in the serializer context.")

		args = [getattr(obj, lookup_field) for lookup_field in self.lookup_fields]
		return reverse(self.view_name, args=args, request=request)