The qtgrpcgen Tool
The qtgrpcgen tool can be used to generate Qt GRPC service classes from a protobuf schema. The tool is provided by the CMake Qt6::GrpcTools package. It works as an extension to Google's protoc tool.
find_package(Qt6 COMPONENTS GrpcTools REQUIRED)
Usage
Qt provides CMake functions that ease the use of the qtgrpcgen tool. When using CMake as a build tool you should prefer using the Qt CMake API. For build systems other than CMake, adapt the commands described in Running qtgrpcgen manually.
Note: there is no explicit support for building gRPC and Protobuf applications using the Qt GRPC module with qmake.
CMake
The following CMake commands integrate a gRPC service into a Qt project.
Generates Qt-based C++ services using a protobuf schema |
Usually qtgrpcgen would be invoked through CMake using the qt_add_grpc macro, as shown in the following example:
cmake_minimum_required(VERSION 3.16...3.22)
project(MyProject)
find_package(Qt6 REQUIRED COMPONENTS Protobuf Grpc)
qt_standard_project_setup()
qt_add_protobuf(MyProtoMessageLib
PROTO_FILES
path/to/helloworld.proto
PROTO_INCLUDES
path/to/proto/include
)
qt_add_grpc(MyGrpcClient CLIENT
PROTO_FILES
path/to/helloworld.proto
PROTO_INCLUDES
path/to/proto/include
)
qt_add_executable(MyApp main.cpp)
target_link_libraries(MyApp PRIVATE MyGrpcClient MyProtoMessageLib Qt6::Protobuf)
The example above calls the qt_add_grpc() CMake function to generate a library called MyGrpcClient.
Note: if the .proto file API contains messages, then the qt_add_protobuf() CMake function should be called to generate protobuf message classes for the project.
Finally, the example creates a target for an executable called MyApp which links to the MyGrpcClient and MyProtoMessageLib libraries.
Running qtgrpcgen manually
protoc --plugin=protoc-gen-qtgrpc=<path/to/bin/>qtgrpcgen \
--qtgrpc_out="[<options>:]<output_dir>" \
[--qtgrpc_opt="<options>"] \
[-I/extra/proto/include/path] \
<protofile>.proto
The options argument is a semicolon-separated list of Options. It can be passed by prepending the options to the output_dir argument, delimited by a colon, or through a separate argument, --qtgrpc_opt. You also can pass the corresponding keys as the QT_GRPC_OPTIONS environment variable. Keys must be presented as a semicolon-separated list:
export QT_GRPC_OPTIONS="COPY_COMMENTS;GENERATE_PACKAGE_SUBFOLDERS;EXTRA_NAMESPACE=MyTopLevelNamespace"
Options
The generator supports options that can be provided to tune generation. Options have direct aliases in the qt_add_grpc function. The following options are supported:
COPY_COMMENTSCopies comments from.protofiles. If provided in the parameter list, comments related to messages and fields are copied to generated header files.GENERATE_PACKAGE_SUBFOLDERSgenerates a folder structure for the generated files matching the.protofile's package name. For examplepackage io.qt.test;would put the generated files intoio/qt/test/.EXTRA_NAMESPACEis 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.protofile. If this option is used then everything will be nested inside the extra namespace.EXPORT_MACROis the base name of the symbol export macro used for the generated code. The generated macro name is constructed asQPB_<EXPORT_MACRO>_EXPORT. If the option is not set, the macro is not generated.