qt_add_grpc

Generates Qt-based C++ services using a protobuf schema

This command was introduced in Qt 6.5.

Usually qtgrpcgen is invoked through the qt_add_grpc CMake macro.

qt_add_grpc(<target> <TARGET_TYPE>
    PROTO_FILES <file> ...
    [COPY_COMMENTS]
    [GENERATE_PACKAGE_SUBFOLDERS]
    [QML]
    [EXTRA_NAMESPACE <namespace>]
    [EXPORT_MACRO <infix>]
    [PROTO_INCLUDES <path> ...]
    [OUTPUT_DIRECTORY <dir>]
    [OUTPUT_HEADERS <var>]
    [OUTPUT_TARGETS <var>]
)

The source files are created by qtgrpcgen and added to the target. If the target already exists, the files are added to the target source list. If the target doesn't exist, it is created as a library which you must link to.

The gRPC library that is generated using the qt_add_grpc command refers to the protobuf symbols that are used in service calls. This means you either need to use a common target in both qt_add_protobuf and qt_add_grpc calls or link the generated protobuf library to the gRPC one.

Considering the above statement you may reuse the target for both protobuf and gRPC client code:

# Generate the protobuf types first
qt_add_protobuf(test_service_client
    PROTO_FILES
        test_service.protobuf
)
...
# Reuse the protobuf target and extend it with gRPC client
# functionality
qt_add_grpc(test_service_client CLIENT
    PROTO_FILES
        test_service.protobuf
)

If you want to have separate targets then you need to link the gRPC client target to the protobuf one:

# Generate the protobuf types first
qt_add_protobuf(test_service_protobuf
    PROTO_FILES
        test_service.protobuf
)
...
# Add separate target with the generated code of the gRPC client.
qt_add_grpc(test_service_client CLIENT
    PROTO_FILES
        test_service.protobuf
)
target_link_libraries(test_service_client PRIVATE test_service_protobuf)

Arguments

• TARGET_TYPE is the type of gRPC code to be generated. Since gRPC supports a client-server architecture, CLIENT or SERVER source code may be generated.

  Note: for Qt 6.5 only CLIENT source code generation is supported.

• QML enables a QmlClient generation. The class is inherited from the base CLIENT class, but extends it with QML_ELEMENT macro, QML properties, and Q_INVOKABLE methods. The result of generation may be added into the QML module, that makes QmlClient available as an object from QML. See example of adding the QmlClient class into QML module below:

  qt_add_protobuf(targetname
      QML
      ...
  )
  qt_add_grpc(targetname
      QML
      ...
  )

  Note: for Qt 6.7 only QmlClient source code generation is supported.

• COPY_COMMENTS copies comments from .proto files. If provided in the parameter list, comments related to messages and fields are copied to generated header files.
• GENERATE_PACKAGE_SUBFOLDERS generates a folder structure for the generated files matching the .proto file's package name. For example, package io.qt.test; would put the generated files into io/qt/test/.
• EXTRA_NAMESPACE is an optional namespace that will be used for the generated classes. The classes are always generated in a namespace whose name is the same as the package name specified in the .proto file. If this option is used, then everything will be nested inside the extra namespace.
• EXPORT_MACRO is the base name of the symbol export macro used for the generated code. The generated macro name is constructed as QPB_<EXPORT_MACRO>_EXPORT. If the option is not set, the macro is not generated.
• PROTO_FILES is the list of .proto files that will be used in the generation procedure.
• PROTO_INCLUDES is the list of directories that will be searched for dependencies.
• OUTPUT_DIRECTORY is the directory where the generated files will be put. By default, the current directory (while evaluating the function) is used.
• OUTPUT_HEADERS can be used to specify a variable that will hold the list of headers created by the function. This list can be useful for custom project install rules.
• OUTPUT_TARGETS can be used to specify a variable that will hold the list of targets created by the function. This list can be useful for custom project install rules.