Field selection mixins for Tastypie (dehydrate, full_dehydrate and db level filter)

fieldSelectMixin

###################################################################
# mixin that utilizes dehydrate to implement field selection      #
# Tested with python 2.7.5, django 1.8 and django-tastypie 0.12.1 #
###################################################################
class fieldSelectMixin(object):
    """
    Mixin to allow field selection, dehydrate method.
    """
    def dehydrate(self, bundle):
        selectedFields = bundle.request.GET.get('fields')
        debug = bundle.request.GET.get('debug', False)

        if selectedFields:
            selectedFields = selectedFields.split(',')
            removedFields = [field for field in bundle.data.keys() if field not in selectedFields]

            for field in removedFields:
                del bundle.data[field]

            if debug:
                bundle.data['selectedFields'] = [field for field in selectedFields if field in bundle.data.keys()]
                bundle.data['removedFields'] = removedFields

        return bundle


###################################################################
# mixin that utilizes full_dehydrate to implement field selection #
# Tested with python 2.7.5, django 1.8 and django-tastypie 0.12.1 #
###################################################################
class fieldSelectMixin(object):
    """
    Mixin to allow field selection, full_dehydrate method.
    """
    def full_dehydrate(self, bundle, for_list=False):
        """
        Given a bundle with an object instance, extract the information from it
        to populate the resource.
        """
        use_in = ['all', 'list' if for_list else 'detail']
 
        # Get values if fields is set in query
        selectedFields = bundle.request.GET.get('fields')
 
        # If selectedFields has data turn it into a list
        if selectedFields:
            selectedFields = selectedFields.split(',')
 
        # Dehydrate each field.
        for field_name, field_object in self.fields.items():
            # If it's not for use in this mode, skip
            field_use_in = getattr(field_object, 'use_in', 'all')
            if callable(field_use_in):
                if not field_use_in(bundle):
                    continue
            else:
                if field_use_in not in use_in:
                    continue
 
            # If fields is set in query paramaters filter field_name
            # and discard any not in selectedFields
            if selectedFields:
                if field_name not in selectedFields:
                    continue
 
            # A touch leaky but it makes URI resolution work.
            if getattr(field_object, 'dehydrated_type', None) == 'related':
                field_object.api_name = self._meta.api_name
                field_object.resource_name = self._meta.resource_name
 
            bundle.data[field_name] = field_object.dehydrate(bundle, for_list=for_list)
 
            # Check for an optional method to do further dehydration.
            method = getattr(self, "dehydrate_%s" % field_name, None)
 
            if method:
                bundle.data[field_name] = method(bundle)
 
        bundle = self.dehydrate(bundle)
        return bundle


###################################################################
# mixin that performs field selection at the db level             #
# Tested with python 2.7.5, django 1.8 and django-tastypie 0.12.1 #
###################################################################
class fieldSelectMixin(object):
    """
    Mixin to allow field selection, db level filter method.
    Tested with python 2.7.5, django 1.8 and django-tastypie 0.12.1.
    """
    def select_fields(self, bundle, queryset):
        """
        Given an optional field list in GET query, tells the model queryset
        to only select a list of fields from db.
        """
        if hasattr(bundle.request, 'GET'):
            selectedFields = bundle.request.GET.get('fields')
            # If selectedFields has data turn it into a list
            if selectedFields:
                selectedFields = selectedFields.split(',')
                queryset = queryset.only(*selectedFields)
        return queryset
 
 
    def full_dehydrate(self, bundle, for_list=False):
        """
        Given a bundle with an object instance, extract the information from it
        to populate the resource.
        """
        use_in = ['all', 'list' if for_list else 'detail']
 
        field_list = self.fields.items()
 
        # Get values if fields is set in query
        if hasattr(bundle.request, 'GET'):
            selectedFields = bundle.request.GET.get('fields')
            # If selectedFields has data turn it into a list
            if selectedFields:
                selectedFields = selectedFields.split(',')
                # Iterate only on the selected fields
                field_list = [(f_n, f_o) for f_n, f_o in field_list if f_n in selectedFields]
 
        # Dehydrate each field.
        for field_name, field_object in field_list:
            # If it's not for use in this mode, skip
            field_use_in = getattr(field_object, 'use_in', 'all')
            if callable(field_use_in):
                if not field_use_in(bundle):
                    continue
            else:
                if field_use_in not in use_in:
                    continue
 
            # A touch leaky but it makes URI resolution work.
            if getattr(field_object, 'dehydrated_type', None) == 'related':
                field_object.api_name = self._meta.api_name
                field_object.resource_name = self._meta.resource_name
 
            bundle.data[field_name] = field_object.dehydrate(bundle, for_list=for_list)
 
            # Check for an optional method to do further dehydration.
            method = getattr(self, "dehydrate_%s" % field_name, None)
 
            if method:
                bundle.data[field_name] = method(bundle)
 
        bundle = self.dehydrate(bundle)
        return bundle
 
 
    def obj_get_list(self, bundle, **kwargs):
        """
        Fetches the list of objects available on the resource.
        This needs to be implemented at the user level.
        ``ModelResource`` includes a full working version specific to Django's
        ``Models``.
        """
        filters = {}
 
        if hasattr(bundle.request, 'GET'):
            # Grab a mutable copy.
            filters = bundle.request.GET.copy()
 
        # Update with the provided kwargs.
        filters.update(kwargs)
        applicable_filters = self.build_filters(filters=filters)
 
        try:
            objects = self.select_fields(bundle, self.apply_filters(bundle.request, applicable_filters))
            return self.authorized_read_list(objects, bundle)
        except ValueError:
            raise BadRequest("Invalid resource lookup (mismatched type).")
 

    def obj_get(self, bundle, **kwargs):
        """
        Fetches an individual object on the resource.
        This needs to be implemented at the user level. If the object can not
        be found, this should raise a ``NotFound`` exception.
        ``ModelResource`` includes a full working version specific to Django's
        ``Models``.
        """
        try:
            object_list = self.select_fields(bundle, self.get_object_list(bundle.request).filter(**kwargs))
            stringified_kwargs = ', '.join(["%s=%s" % (k, v) for k, v in kwargs.items()])
 
            if len(object_list) <= 0:
                raise self._meta.object_class.DoesNotExist("Couldn't find an instance of '%s' which matched '%s'." % (self._meta.object_class.__name__, stringified_kwargs))
            elif len(object_list) > 1:
                raise MultipleObjectsReturned("More than '%s' matched '%s'." % (self._meta.object_class.__name__, stringified_kwargs))
 
            bundle.obj = object_list[0]
            self.authorized_read_detail(object_list, bundle)
            return bundle.obj
        except ValueError:
            raise NotFound("Invalid resource lookup (mismatched type).")