rest_flex_fields2.serializers.FlexFieldsSerializerMixin
=======================================================

.. py:class:: rest_flex_fields2.serializers.FlexFieldsSerializerMixin(*args, **kwargs)

   Bases: :py:obj:`rest_framework.serializers.Serializer`


   Mixin that adds sparse-fieldset and nested-expansion support to a serializer.

   Accepts the ``fields``, ``omit``, and ``expand`` keyword arguments (names
   are configurable via ``REST_FLEX_FIELDS2`` settings) both as constructor
   kwargs and as query-string parameters on the current request.  Query
   parameters are only read on the root serializer; nested serializers
   receive their options through constructor kwargs propagated by the parent.

   Declare expandable relations either on ``Meta.expandable_fields`` (preferred)
   or directly on ``expandable_fields`` for backwards compatibility.


   .. py:attribute:: expandable_fields


   .. py:attribute:: maximum_expansion_depth
      :type:  Optional[int]
      :value: None



   .. py:attribute:: recursive_expansion_permitted
      :type:  Optional[bool]
      :value: None



   .. py:attribute:: parent


   .. py:attribute:: expanded_fields
      :value: []



   .. py:method:: get_maximum_expansion_depth()

      Return the effective maximum expansion depth.

      Uses the serializer-level ``maximum_expansion_depth`` attribute when
      set, otherwise falls back to the ``MAXIMUM_EXPANSION_DEPTH`` setting.



   .. py:method:: get_recursive_expansion_permitted()

      Return whether recursive expansion is allowed.

      Uses the serializer-level ``recursive_expansion_permitted`` attribute
      when set, otherwise falls back to the ``RECURSIVE_EXPANSION_PERMITTED``
      setting.



   .. py:method:: to_representation(instance)

      Apply request-sourced flex-fields options once, then delegate to super.



   .. py:method:: get_fields()

      Return fields after applying constructor-sourced flex-fields options.



   .. py:method:: apply_flex_fields(fields, flex_options)

      Apply sparse-fieldset and expansion options to `fields` in place.

      Removes fields that are excluded by ``omit`` or not present in
      ``fields`` (sparse-fieldset), then replaces fields listed in
      ``expand`` with their nested serializer instances.
      Returns the modified `fields` mapping.



   .. py:method:: recursive_expansion_not_permitted()

      Raise a validation error indicating recursive expansion.

      Override this method to raise a custom exception instead of the
      default ``ValidationError``.



   .. py:method:: expansion_depth_exceeded()

      Raise a validation error indicating the expansion depth limit was exceeded.

      Override this method to raise a custom exception instead of the
      default ``ValidationError``.