The qtprotobufgen Tool▲
The qtprotobufgen tool can be used to generate QtProtobuf classes from a protobuf schema. The tool is provided by the CMake Qt6::ProtobufTools package. It works as an extension to Google's protoc tool.
find_package(Qt6 COMPONENTS ProtobufTools REQUIRED)I. Usage▲
Qt provides CMake functions that ease the use of the qtprotobufgen 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 manually.
there is no explicit support for building gRPC and Protobuf applications using the Qt GRPC module with qmake.
I-1. CMake▲
The following CMake commands integrate a protobuf schema into a Qt project.
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qt_add_protobuf: Generates Qt-based C++ source code using a protobuf schema
Usually qtprotobufgen would be invoked through CMake using the qt_add_protobuf macro, as shown in the following example:
cmake_minimum_required(VERSION 3.16...3.22)
project(MyThings)
find_package(Qt6 REQUIRED COMPONENTS Protobuf)
qt_standard_project_setup()
qt_add_protobuf(MyMessages
GENERATE_PACKAGE_SUBFOLDERS
PROTO_FILES
path/to/message.proto
path/to/other_message.proto
PROTO_INCLUDES
/path/to/proto/include
)
qt_add_executable(MyApp main.cpp)
target_link_libraries(MyApp PRIVATE MyMessages)In the example above we generate a library called MyMessages which contains the message types defined in the paths passed to the PROTO_FILES option. We use the GENERATE_PACKAGE_SUBFOLDERS option to generate a folder structure for the generated files. And the PROTO_INCLUDES option tells protoc to look for dependencies/imports in the specified directories.
We then create a target for an executable called MyApp which we link to the MyMessages library.
I-2. Running manually▲
protoc --plugin=protoc-gen-qtprotobuf=<path/to/bin/>qtprotobufgen \
--qtprotobuf_out="[<options>:]<output_dir>" \
[--qtprotobuf_opt="<options>"] \
[-I/extra/proto/include/path] \
<protofile>.protoThe options argument is a semicolon-separated list of Options. It can be passed in two different ways. Either by prepending to the options to the output_dir argument, delimited by a colon. Or through a separate argument, --qtprotobuf_opt. You also can pass the corresponding keys as the QT_PROTOBUF_OPTIONS environment variable. Keys need to be presented as a semicolon-separated list:
export QT_PROTOBUF_OPTIONS="COPY_COMMENTS;GENERATE_PACKAGE_SUBFOLDERS;EXTRA_NAMESPACE=MyTopLevelNamespace"I-3. Options▲
The generator supports options that can be provided to tune generation. Options have direct aliases in the qt_add_protobuf function. The following options are supported:
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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.
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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/.
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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.
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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.