Final bits of docs for ModelSerializer fields API

lovelydinosaur · lovelydinosaur · commit 2a1485e00943 · 2014-12-19T21:32:43.000Z
diff --git a/docs/api-guide/serializers.md b/docs/api-guide/serializers.md
@@ -457,7 +457,7 @@ To do so, open the Django shell, using `python manage.py shell`, then import the
         name = CharField(allow_blank=True, max_length=100, required=False)
         owner = PrimaryKeyRelatedField(queryset=User.objects.all())
 
-## Specifying which fields should be included
+## Specifying which fields to include
 
 If you only want a subset of the default fields to be used in a model serializer, you can do so using `fields` or `exclude` options, just as you would with a `ModelForm`.
 
@@ -499,7 +499,7 @@ You can add extra fields to a `ModelSerializer` or override the default fields b
 
 Extra fields can correspond to any property or callable on the model.
 
-## Specifying which fields should be read-only
+## Specifying read only fields
 
 You may wish to specify multiple fields as read-only. Instead of adding each field explicitly with the `read_only=True` attribute, you may use the shortcut Meta option, `read_only_fields`.
 
@@ -528,7 +528,7 @@ Please review the [Validators Documentation](/api-guide/validators/) for details
 ---
 
 
-## Specifying additional keyword arguments for fields.
+## Additional keyword arguments
 
 There is also a shortcut allowing you to specify arbitrary additional keyword arguments on fields, using the `extra_kwargs` option. Similarly to `read_only_fields` this means you do not need to explicitly declare the field on the serializer.
 
@@ -567,31 +567,62 @@ The inner `Meta` class on serializers is not inherited from parent classes by de
 
 Typically we would recommend *not* using inheritance on inner Meta classes, but instead declaring all options explicitly.
 
-## Advanced `ModelSerializer` usage
+## Customizing field mappings
 
 The ModelSerializer class also exposes an API that you can override in order to alter how serializer fields are automatically determined when instantiating the serializer.
 
-#### `.serializer_field_mapping`
+Normally if a `ModelSerializer` does not generate the fields you need by default the you should either add them to the class explicitly, or simply use a regular `Serializer` class instead. However in some cases you may want to create a new base class that defines how the serializer fields are created for any given model.
+
+### `.serializer_field_mapping`
 
 A mapping of Django model classes to REST framework serializer classes. You can override this mapping to alter the default serializer classes that should be used for each model class.
 
-#### `.serializer_relational_field`
+### `.serializer_relational_field`
 
 This property should be the serializer field class, that is used for relational fields by default. For `ModelSerializer` this defaults to `PrimaryKeyRelatedField`. For `HyperlinkedModelSerializer` this defaults to `HyperlinkedRelatedField`.
 
-#### The build field methods
+### The field_class and field_kwargs API
+
+The following methods are called to determine the class and keyword arguments for each field that should be automatically included on the serializer. Each of these methods should return a two tuple of `(field_class, field_kwargs)`.
+
+### `.build_standard_field(self, field_name, model_field)`
+
+Called to generate a serializer field that maps to a standard model field.
+
+The default implementation returns a serializer class based on the `serializer_field_mapping` attribute.
+
+### `.build_relational_field(self, field_name, relation_info)`
+
+Called to generate a serializer field that maps to a relational model field.
+
+The default implementation returns a serializer class based on the `serializer_relational_field` attribute.
+
+The `relation_info` argument is a named tuple, that contains `model_field`, `related_model`, `to_many` and `has_through_model` properties.
+
+### `.build_nested_field(self, field_name, relation_info, nested_depth)`
+
+Called to generate a serializer field that maps to a relational model field, when the `depth` option has been set.
+
+The default implementation dynamically creates a nested serializer class based on either `ModelSerializer` or `HyperlinkedModelSerializer`.
+
+The `nested_depth` will be the value of the `depth` option, minus one.
+
+The `relation_info` argument is a named tuple, that contains `model_field`, `related_model`, `to_many` and `has_through_model` properties.
+
+### `.build_property_field(self, field_name, model_class)`
 
-#### `build_standard_field(**kwargs)`
+Called to generate a serializer field that maps to a property or zero-argument method on the model class.
 
-#### `build_relational_field(**kwargs)`
+The default implementation returns a `ReadOnlyField` class.
 
-#### `build_nested_field(**kwargs)`
+### `.build_url_field(self, field_name, model_class)`
 
-#### `build_property_field(**kwargs)`
+Called to generate a serializer field for the serializer's own `url` field. The default implementation returns a `HyperlinkedIdentityField` class.
 
-#### `build_url_field(**kwargs)`
+### `.build_unknown_field(self, field_name, model_class)`
 
-#### `build_unknown_field(**kwargs)`
+Called when the field name did not map to any model field or model property.
+The default implementation raises an error, although subclasses may customize this behavior.
 
 ---
 
diff --git a/docs_theme/css/default.css b/docs_theme/css/default.css
@@ -239,6 +239,10 @@ body a:hover{
      }
 }
 
+h1 code, h2 code, h3 code, h4 code, h5 code {
+  color: #333;
+}
+
 /* sticky footer and footer */
 html, body {
   height: 100%;
diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
@@ -802,10 +802,25 @@ def get_fields(self):
         Return the dict of field names -> field instances that should be
         used for `self.fields` when instantiating the serializer.
         """
+        assert hasattr(self, 'Meta'), (
+            'Class {serializer_class} missing "Meta" attribute'.format(
+                serializer_class=self.__class__.__name__
+            )
+        )
+        assert hasattr(self.Meta, 'model'), (
+            'Class {serializer_class} missing "Meta.model" attribute'.format(
+                serializer_class=self.__class__.__name__
+            )
+        )
+
         declared_fields = copy.deepcopy(self._declared_fields)
         model = getattr(self.Meta, 'model')
         depth = getattr(self.Meta, 'depth', 0)
 
+        if depth is not None:
+            assert depth >= 0, "'depth' may not be negative."
+            assert depth <= 10, "'depth' may not be greater than 10."
+
         # Retrieve metadata about fields & relationships on the model class.
         info = model_meta.get_field_info(model)
         field_names = self.get_field_names(declared_fields, info)
@@ -817,27 +832,32 @@ def get_fields(self):
             field_names, declared_fields, extra_kwargs
         )
 
-        # Now determine the fields that should be included on the serializer.
-        ret = OrderedDict()
+        # Determine the fields that should be included on the serializer.
+        fields = OrderedDict()
+
         for field_name in field_names:
+            # If the field is explicitly declared on the class then use that.
             if field_name in declared_fields:
-                # Field is explicitly declared on the class, use that.
-                ret[field_name] = declared_fields[field_name]
+                fields[field_name] = declared_fields[field_name]
                 continue
 
             # Determine the serializer field class and keyword arguments.
-            field_cls, kwargs = self.build_field(field_name, info, model, depth)
+            field_class, field_kwargs = self.build_field(
+                field_name, info, model, depth
+            )
 
-            # Populate any kwargs defined in `Meta.extra_kwargs`
-            kwargs = self.build_field_kwargs(kwargs, extra_kwargs, field_name)
+            # Include any kwargs defined in `Meta.extra_kwargs`
+            field_kwargs = self.build_field_kwargs(
+                field_kwargs, extra_kwargs, field_name
+            )
 
             # Create the serializer field.
-            ret[field_name] = field_cls(**kwargs)
+            fields[field_name] = field_class(**field_kwargs)
 
         # Add in any hidden fields.
-        ret.update(hidden_fields)
+        fields.update(hidden_fields)
 
-        return ret
+        return fields
 
     # Methods for determining the set of field names to include...
 
@@ -916,108 +936,105 @@ def get_default_field_names(self, declared_fields, model_info):
 
     # Methods for constructing serializer fields...
 
-    def build_field(self, field_name, info, model, nested_depth):
+    def build_field(self, field_name, info, model_class, nested_depth):
         """
         Return a two tuple of (cls, kwargs) to build a serializer field with.
         """
         if field_name in info.fields_and_pk:
-            return self.build_standard_field(field_name, info, model)
+            model_field = info.fields_and_pk[field_name]
+            return self.build_standard_field(field_name, model_field)
 
         elif field_name in info.relations:
+            relation_info = info.relations[field_name]
             if not nested_depth:
-                return self.build_relational_field(field_name, info, model)
+                return self.build_relational_field(field_name, relation_info)
             else:
-                return self.build_nested_field(field_name, info, model, nested_depth)
+                return self.build_nested_field(field_name, relation_info, nested_depth)
 
-        elif hasattr(model, field_name):
-            return self.build_property_field(field_name, info, model)
+        elif hasattr(model_class, field_name):
+            return self.build_property_field(field_name, model_class)
 
         elif field_name == api_settings.URL_FIELD_NAME:
-            return self.build_url_field(field_name, info, model)
+            return self.build_url_field(field_name, model_class)
 
-        return self.build_unknown_field(field_name, info, model)
+        return self.build_unknown_field(field_name, model_class)
 
-    def build_standard_field(self, field_name, info, model):
+    def build_standard_field(self, field_name, model_field):
         """
         Create regular model fields.
         """
         field_mapping = ClassLookupDict(self.serializer_field_mapping)
-        model_field = info.fields_and_pk[field_name]
 
-        field_cls = field_mapping[model_field]
-        kwargs = get_field_kwargs(field_name, model_field)
+        field_class = field_mapping[model_field]
+        field_kwargs = get_field_kwargs(field_name, model_field)
 
-        if 'choices' in kwargs:
+        if 'choices' in field_kwargs:
             # Fields with choices get coerced into `ChoiceField`
             # instead of using their regular typed field.
-            field_cls = ChoiceField
-        if not issubclass(field_cls, ModelField):
+            field_class = ChoiceField
+        if not issubclass(field_class, ModelField):
             # `model_field` is only valid for the fallback case of
             # `ModelField`, which is used when no other typed field
             # matched to the model field.
-            kwargs.pop('model_field', None)
-        if not issubclass(field_cls, CharField) and not issubclass(field_cls, ChoiceField):
+            field_kwargs.pop('model_field', None)
+        if not issubclass(field_class, CharField) and not issubclass(field_class, ChoiceField):
             # `allow_blank` is only valid for textual fields.
-            kwargs.pop('allow_blank', None)
+            field_kwargs.pop('allow_blank', None)
 
-        return field_cls, kwargs
+        return field_class, field_kwargs
 
-    def build_relational_field(self, field_name, info, model):
+    def build_relational_field(self, field_name, relation_info):
         """
         Create fields for forward and reverse relationships.
         """
-        relation_info = info.relations[field_name]
-
-        field_cls = self.serializer_related_class
-        kwargs = get_relation_kwargs(field_name, relation_info)
+        field_class = self.serializer_related_class
+        field_kwargs = get_relation_kwargs(field_name, relation_info)
 
         # `view_name` is only valid for hyperlinked relationships.
-        if not issubclass(field_cls, HyperlinkedRelatedField):
-            kwargs.pop('view_name', None)
+        if not issubclass(field_class, HyperlinkedRelatedField):
+            field_kwargs.pop('view_name', None)
 
-        return field_cls, kwargs
+        return field_class, field_kwargs
 
-    def build_nested_field(self, field_name, info, model, nested_depth):
+    def build_nested_field(self, field_name, relation_info, nested_depth):
         """
         Create nested fields for forward and reverse relationships.
         """
-        relation_info = info.relations[field_name]
-
         class NestedSerializer(ModelSerializer):
             class Meta:
-                model = relation_info.related
-                depth = nested_depth - 1
+                model = relation_info.related_model
+                depth = nested_depth
 
-        field_cls = NestedSerializer
-        kwargs = get_nested_relation_kwargs(relation_info)
+        field_class = NestedSerializer
+        field_kwargs = get_nested_relation_kwargs(relation_info)
 
-        return field_cls, kwargs
+        return field_class, field_kwargs
 
-    def build_property_field(self, field_name, info, model):
+    def build_property_field(self, field_name, model_class):
         """
         Create a read only field for model methods and properties.
         """
-        field_cls = ReadOnlyField
-        kwargs = {}
+        field_class = ReadOnlyField
+        field_kwargs = {}
 
-        return field_cls, kwargs
+        return field_class, field_kwargs
 
-    def build_url_field(self, field_name, info, model):
+    def build_url_field(self, field_name, model_class):
         """
         Create a field representing the object's own URL.
         """
-        field_cls = HyperlinkedIdentityField
-        kwargs = get_url_kwargs(model)
+        field_class = HyperlinkedIdentityField
+        field_kwargs = get_url_kwargs(model_class)
 
-        return field_cls, kwargs
+        return field_class, field_kwargs
 
-    def build_unknown_field(self, field_name, info, model):
+    def build_unknown_field(self, field_name, model_class):
         """
         Raise an error on any unknown fields.
         """
         raise ImproperlyConfigured(
             'Field name `%s` is not valid for model `%s`.' %
-            (field_name, model.__class__.__name__)
+            (field_name, model_class.__name__)
         )
 
     def build_field_kwargs(self, kwargs, extra_kwargs, field_name):
@@ -1318,17 +1335,16 @@ def get_default_field_names(self, declared_fields, model_info):
             list(model_info.forward_relations.keys())
         )
 
-    def build_nested_field(self, field_name, info, model, nested_depth):
+    def build_nested_field(self, field_name, relation_info, nested_depth):
         """
         Create nested fields for forward and reverse relationships.
         """
-        relation_info = info.relations[field_name]
-
         class NestedSerializer(HyperlinkedModelSerializer):
             class Meta:
-                model = relation_info.related
+                model = relation_info.related_model
                 depth = nested_depth - 1
 
-        field_cls = NestedSerializer
-        kwargs = get_nested_relation_kwargs(relation_info)
-        return field_cls, kwargs
+        field_class = NestedSerializer
+        field_kwargs = get_nested_relation_kwargs(relation_info)
+
+        return field_class, field_kwargs
diff --git a/rest_framework/utils/model_meta.py b/rest_framework/utils/model_meta.py
@@ -24,7 +24,7 @@
 
 RelationInfo = namedtuple('RelationInfo', [
     'model_field',
-    'related',
+    'related_model',
     'to_many',
     'has_through_model'
 ])
@@ -77,7 +77,7 @@ def get_field_info(model):
     for field in [field for field in opts.fields if field.serialize and field.rel]:
         forward_relations[field.name] = RelationInfo(
             model_field=field,
-            related=_resolve_model(field.rel.to),
+            related_model=_resolve_model(field.rel.to),
             to_many=False,
             has_through_model=False
         )
@@ -86,7 +86,7 @@ def get_field_info(model):
     for field in [field for field in opts.many_to_many if field.serialize]:
         forward_relations[field.name] = RelationInfo(
             model_field=field,
-            related=_resolve_model(field.rel.to),
+            related_model=_resolve_model(field.rel.to),
             to_many=True,
             has_through_model=(
                 not field.rel.through._meta.auto_created
@@ -99,7 +99,7 @@ def get_field_info(model):
         accessor_name = relation.get_accessor_name()
         reverse_relations[accessor_name] = RelationInfo(
             model_field=None,
-            related=relation.model,
+            related_model=relation.model,
             to_many=relation.field.rel.multiple,
             has_through_model=False
         )
@@ -109,7 +109,7 @@ def get_field_info(model):
         accessor_name = relation.get_accessor_name()
         reverse_relations[accessor_name] = RelationInfo(
             model_field=None,
-            related=relation.model,
+            related_model=relation.model,
             to_many=True,
             has_through_model=(
                 (getattr(relation.field.rel, 'through', None) is not None)
diff --git a/tests/test_model_serializer.py b/tests/test_model_serializer.py

Original file line number	Diff line number	Diff line change
`@@ -239,6 +239,10 @@ body a:hover{`
`239`	`239`	`}`
`240`	`240`	`}`
`241`	`241`
	`242`	`+h1 code, h2 code, h3 code, h4 code, h5 code {`
	`243`	`+ color: #333;`
	`244`	`+}`
	`245`	`+`
`242`	`246`	`/* sticky footer and footer */`
`243`	`247`	`html, body {`
`244`	`248`	`height: 100%;`