FieldMask class

FieldMask represents a set of symbolic field paths, for example:

 paths: "f.a"
 paths: "f.b.d"

Here f represents a field in some root message, a and b fields in the message found in f, and d a field found in the message in f.b.

Field masks are used to specify a subset of fields that should be returned by a get operation or modified by an update operation. Field masks also have a custom JSON encoding (see below).

Field Masks in Projections

When used in the context of a projection, a response message or sub-message is filtered by the API to only contain those fields as specified in the mask. For example, if the mask in the previous example is applied to a response message as follows:

 f {
   a : 22
   b {
     d : 1
     x : 2
   }
   y : 13
 }
 z: 8

The result will not contain specific values for fields x,y and z (their value will be set to the default, and omitted in proto text output):

 f {
   a : 22
   b {
     d : 1
   }
 }

A repeated field is not allowed except at the last position of a paths string.

If a FieldMask object is not present in a get operation, the operation applies to all fields (as if a FieldMask of all fields had been specified).

Note that a field mask does not necessarily apply to the top-level response message. In case of a REST get operation, the field mask applies directly to the response, but in case of a REST list operation, the mask instead applies to each individual message in the returned resource list. In case of a REST custom method, other definitions may be used. Where the mask applies will be clearly documented together with its declaration in the API. In any case, the effect on the returned resource/resources is required behavior for APIs.

Field Masks in Update Operations

A field mask in update operations specifies which fields of the targeted resource are going to be updated. The API is required to only change the values of the fields as specified in the mask and leave the others untouched. If a resource is passed in to describe the updated values, the API ignores the values of all fields not covered by the mask.

If a repeated field is specified for an update operation, new values will be appended to the existing repeated field in the target resource. Note that a repeated field is only allowed in the last position of a paths string.

If a sub-message is specified in the last position of the field mask for an update operation, then new value will be merged into the existing sub-message in the target resource.

For example, given the target message:

 f {
   b {
     d: 1
     x: 2
   }
   c: [1]
 }

And an update message:

 f {
   b {
     d: 10
   }
   c: [2]
 }

then if the field mask is:

paths: "f.b", "f.c"

then the result will be:

 f {
   b {
     d: 10
     x: 2
   }
   c: [1, 2]
 }

An implementation may provide options to override this default behavior for repeated and message fields.

In order to reset a field's value to the default, the field must be in the mask and set to the default value in the provided resource. Hence, in order to reset all fields of a resource, provide a default instance of the resource and set all fields in the mask, or do not provide a mask as described below.

If a field mask is not present on update, the operation applies to all fields (as if a field mask of all fields has been specified). Note that in the presence of schema evolution, this may mean that fields the client does not know and has therefore not filled into the request will be reset to their default. If this is unwanted behavior, a specific service may require a client to always specify a field mask, producing an error if not.

As with get operations, the location of the resource which describes the updated values in the request message depends on the operation kind. In any case, the effect of the field mask is required to be honored by the API.

Considerations for HTTP REST

The HTTP kind of an update operation which uses a field mask must be set to PATCH instead of PUT in order to satisfy HTTP semantics (PUT must only be used for full updates).

JSON Encoding of Field Masks

In JSON, a field mask is encoded as a single string where paths are separated by a comma. Fields name in each path are converted to/from lower-camel naming conventions.

As an example, consider the following message declarations:

 message Profile {
   User user = 1;
   Photo photo = 2;
 }
 message User {
   string display_name = 1;
   string address = 2;
 }

In proto a field mask for Profile may look as such:

 mask {
   paths: "user.display_name"
   paths: "photo"
 }

In JSON, the same mask is represented as below:

 {
   mask: "user.displayName,photo"
 }

Field Masks and Oneof Fields

Field masks treat fields in oneofs just as regular fields. Consider the following message:

 message SampleMessage {
   oneof test_oneof {
     string name = 4;
     SubMessage sub_message = 9;
   }
 }

The field mask can be:

 mask {
   paths: "name"
 }

Or:

 mask {
   paths: "sub_message"
 }

Note that oneof type names ("test_oneof" in this case) cannot be used in paths.

Field Mask Verification

The implementation of any API method which has a FieldMask type field in the request should verify the included field paths, and return an INVALID_ARGUMENT error if any path is unmappable.

Inheritance

Object
GeneratedMessage
FieldMask

Constructors

FieldMask({Iterable<String>? paths}): factory
FieldMask.fromBuffer(List<int> i, [ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]): factory
FieldMask.fromJson(String i, [ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]): factory

Properties

eventPlugin → EventPlugin?: Subclasses can override this getter to be notified of changes to protobuf fields.
no setterinherited
hashCode → int: Calculates a hash code based on the contents of the protobuf.
no setterinherited
info_ → BuilderInfo: no setteroverride
isFrozen → bool: Returns true if this message is marked read-only. Otherwise false.
no setterinherited
paths → List<String>: The set of field mask paths.
no setter
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
unknownFields → UnknownFieldSet: no setterinherited

Methods

addExtension(Extension extension, Object? value) → void: Adds an extension field value to a repeated field.
inherited
check() → void: inherited
clear() → void: Clears all data that was set in this message.
inherited
clearExtension(Extension extension) → void: Clears an extension field and also removes the extension.
inherited
clearField(int tagNumber) → void: Clears the contents of a given field.
inherited
clone() → FieldMask: Creates a deep copy of the fields in this message. (The generated code uses mergeFromMessage.)
override
copyWith(void updates(FieldMask)) → FieldMask: Apply updates to a copy of this message.
override
createEmptyInstance() → FieldMask: Creates an empty instance of the same message type as this.
override
createMapField<K, V>(int tagNumber, MapFieldInfo<K, V> fi) → Map<K, V>: Creates a Map representing a map field.
inherited
createRepeatedField<T>(int tagNumber, FieldInfo<T> fi) → List<T>: Creates List implementing a mutable repeated field.
inherited
extensionsAreInitialized() → bool: inherited
freeze() → GeneratedMessage: Make this message read-only.
inherited
getDefaultForField(int tagNumber) → dynamic: Returns the default value for the given field.
inherited
getExtension(Extension extension) → dynamic: Returns the value of extension.
inherited
getField(int tagNumber) → dynamic: Returns the value of the field associated with tagNumber, or the default value if it is not set.
inherited
getFieldOrNull(int tagNumber) → dynamic: Returns the value of a field, ignoring any defaults.
inherited
getTagNumber(String fieldName) → int?: inherited
hasExtension(Extension extension) → bool: Returns true if a value of extension is present.
inherited
hasField(int tagNumber) → bool: Whether this message has a field associated with tagNumber.
inherited
hasRequiredFields() → bool: Whether the message has required fields.
inherited
isInitialized() → bool: Whether all required fields in the message and embedded messages are set.
inherited
mergeFromBuffer(List<int> input, [ExtensionRegistry extensionRegistry = ExtensionRegistry.EMPTY]) → void: Merges serialized protocol buffer data into this message.
inherited
mergeFromCodedBufferReader(CodedBufferReader input, [ExtensionRegistry extensionRegistry = ExtensionRegistry.EMPTY]) → void: inherited
mergeFromJson(String data, [ExtensionRegistry extensionRegistry = ExtensionRegistry.EMPTY]) → void: Merges field values from data, a JSON object, encoded as described by GeneratedMessage.writeToJson.
inherited
mergeFromJsonMap(Map<String, dynamic> json, [ExtensionRegistry extensionRegistry = ExtensionRegistry.EMPTY]) → void: Merges field values from a JSON object represented as a Dart map.
inherited
mergeFromMessage(GeneratedMessage other) → void: Merges the contents of the other into this message.
inherited
mergeFromProto3Json(Object? json, {TypeRegistry typeRegistry = const TypeRegistry.empty(), bool ignoreUnknownFields = false, bool supportNamesWithUnderscores = true, bool permissiveEnums = false}) → void: Merges field values from json, a JSON object using proto3 encoding.
inherited
mergeUnknownFields(UnknownFieldSet unknownFieldSet) → void: inherited
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
setExtension(Extension extension, Object value) → void: Sets the value of a non-repeated extension field to value.
inherited
setField(int tagNumber, Object value) → void: Sets the value of a field by its tagNumber.
inherited
toBuilder() → GeneratedMessage: Creates a writable, shallow copy of this message.
inherited
toDebugString() → String: Returns a String representation of this message.
inherited
toProto3Json({TypeRegistry typeRegistry = const TypeRegistry.empty()}) → Object?: Returns an Object representing Proto3 JSON serialization of this.
inherited
toString() → String: Returns a String representation of this message.
inherited
writeToBuffer() → Uint8List: inherited
writeToCodedBufferWriter(CodedBufferWriter output) → void: inherited
writeToJson() → String: Returns a JSON string that encodes this message.
inherited
writeToJsonMap() → Map<String, dynamic>: Returns the JSON encoding of this message as a Dart Map.
inherited

Operators

operator ==(Object other) → bool: The equality operator.
inherited

Static Methods

create() → FieldMask
createRepeated() → PbList<FieldMask>
getDefault() → FieldMask