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, it's better to utilize the Qt CMake API. For build systems other than CMake, you can adjust the commands outlined in the 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 adding options
to the --qtgrpc_out
argument, separated 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"
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_COMMENTS
copies comments from the.proto
files into the generated code.GENERATE_PACKAGE_SUBFOLDERS
uses the package name specifier from the.proto
files to create the folder structure for the generated files. For example, if the package is defined as:package io.qt.test
, the generated files will be placed in OUTPUT_DIRECTORY/io/qt/test/.EXPORT_MACRO
defines the base name for the export macro used in the generated code. The final macro name is constructed asQPB_<EXPORT_MACRO>_EXPORT
. If this option is not set, no export macro is generated.Since Qt 6.8, the following format is supported:
EXPORT_MACRO=macro_name[:macro_output_file[:<true|false>]]
. This format allows you to specify the name of the header file containing the export macro and explicitly control whether it is generated.Note: If <macro_output_file> is not provided, the option defaults to the previous syntax.
QML
enables the generation of a QML client for the gRPC service.
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