Qt Protobuf Well-Known Types C++ Classes

Detailed Description

QtProtobufWellKnownTypes contains the following Protobuf Well-Known types: Supported types:

• Any (message)
• Api (message)
• BoolValue (message)
• BytesValue (message)
• DoubleValue (message)
• Duration (message)
• Empty (message)
• Enum (message)
• EnumValue (message)
• Field (message)
• Field.Cardinality (enum)
• Field.Kind (enum)
• FieldMask (message)
• FloatValue (message)
• Int32Value (message)
• Int64Value (message)
• ListValue (message)
• Method (message)
• Mixin (message)
• NullValue (enum)
• Option (message)
• SourceContext (message)
• StringValue (message)
• Struct (message)
• Syntax (enum)
• Timestamp (message)
• Type (message)
• UInt32Value (message)
• UInt64Value (message)
• Value (message)

Using the ProtobufWellKnownTypes library

To use well-known type in your project you may include the corresponding google .proto file in your interface:

 syntax = "proto3";
 package somepackage;
 import "google/protobuf/any.proto";
 message Message {
     google.protobuf.Any payload = 1;
 }

To use the types listed you must link with the ProtobufWellKnownTypes library by adding the following line to your CMakeLists.txt file:

 target_link_libraries(YourTargetName PRIVATE Qt::ProtobufWellKnownTypes)

Adding QML support for ProtobufWellKnownTypes

The ProtobufWellKnownTypes library doesn't provide the QML support. Although the support will be implemented in future releases, for now you can extend the Qt Protobuf well-known types into QML-compatible types using the following instructions. For example, Empty is often used as an input or output for RPC methods. See below:

 syntax = "proto3";
 package qtgrpc.examples;
 import "google/protobuf/empty.proto";
 service ExampleService {
     rpc emptyMethod(google.protobuf.Empty) returns (google.protobuf.Empty) {}
 }

To call emptyMethod from QML, declare the google.protobuf.Empty type by adding the following code to a header file .h file of the project:

 #include "google/protobuf/empty.qpb.h"

 struct GoogleProtobufAPI
 {
     Q_GADGET
     QML_FOREIGN(google::protobuf::Empty)
     QML_STRUCTURED_VALUE
     QML_VALUE_TYPE(protobufEmpty)
 };

After, you can then use the protobufEmpty value type in QML. See the example below:

 import qtgrpc.examples
 import QtQuick
 import QtGrpc

 Item {
     id: root
     property protobufEmpty value: null

     ServiceClient {
         id: grpcClient
         channel: grpcChannel.channel
     }

     Item {
         Component.onCompleted: {
             grpcClient.emptyMethod(value, messageCallback, errorCallback, grpcCallOptions);
         }
     }
 }

The QML_STRUCTURED_VALUE macro also enables this syntax:

 Component.onCompleted: {
     grpcClient.emptyMethod({}, messageCallback, errorCallback, grpcCallOptions);
 }