qt_wrap_cpp

Creates .moc files from sources.

The command is defined in the Core component of the Qt6 package, which can be loaded like so:

 find_package(Qt6 REQUIRED COMPONENTS Core)

This command was introduced in Qt 5.0.

Synopsis

qt_wrap_cpp supports two signatures. The first signature was added in Qt 6.8 and has the following form:

 qt_wrap_cpp(<TARGET> src_file1 [src_file2 ...]
             [OPTIONS ...]
             [DEPENDS ...])

 qt_wrap_cpp(<VAR> src_file1 [src_file2 ...]
             [TARGET target]
             [OPTIONS ...]
             [DEPENDS ...])

If versionless commands are disabled, use qt6_wrap_cpp() instead. It supports the same set of arguments as this command.

Description

Creates rules for calling the Meta-Object Compiler (moc) on the given source files. For each input file, an output file is generated in the build directory. The paths of the generated files are added to <VAR>.

Arguments

You can set an explicit TARGET. This will make sure that the target properties INCLUDE_DIRECTORIES and COMPILE_DEFINITIONS are also used when scanning the source files with moc.

Since Qt 6.8, when a source file is passed to qt_wrap_cpp instead of a header file to generate a .moc file for a target, the TARGET parameter is needed to set the correct include path for the generated .moc file in the source file. As generated .moc files are added to the target's sources by qt_wrap_cpp, they are not added to <VAR>.

You can set additional OPTIONS that should be added to the moc calls. You can find possible options in the moc documentation.

The OPTIONS can evaluate generator expressions when TARGET is set.

DEPENDS allows you to add additional dependencies for recreation of the generated files. This is useful when the sources have implicit dependencies, like code for a Qt plugin that includes a .json file using the Q_PLUGIN_METADATA() macro.

Examples

Since Qt 6.8:

 qt_add_executable(myapp myapp.cpp main.cpp)
 qt_wrap_cpp(myapp myapp.cpp)

 // myapp.cpp
 #include "myapp.h"
 #include <QObject>

 class MyApp : public QObject {
     Q_OBJECT
 public:
     MyApp() = default;
 };

 #include "myapp.moc"

In the above file, myapp.moc is included in myapp.cpp. To generate the myapp.moc file, the qt_wrap_cpp macro is used with the TARGET parameter. The .moc file and its path will be added to the target's sources and include directories by the qt_wrap_cpp macro.

The old version:

 set(SOURCES myapp.cpp main.cpp)
 qt_wrap_cpp(SOURCES myapp.h)
 qt_add_executable(myapp ${SOURCES})

In the following example, the generator expressions passed to OPTIONS will be evaluated since TARGET is set. The argument is specified this way to avoid syntax errors in the generator expressions.

 set(SOURCES myapp.cpp main.cpp)
 qt_wrap_cpp(SOURCES myapp.h
             TARGET myapp
             OPTIONS
             "$<$<CONFIG:Debug>:-DMY_OPTION_FOR_DEBUG>"
             "-DDEFINE_CMDLINE_SIGNAL=void cmdlineSignal(const QMap<int, int> &i)"
             "$<$<CONFIG:Debug>:-DDEFINE_CMDLINE_SIGNAL_IN_GENEX=void cmdlineSignal(const QMap<int$<COMMA> int$<ANGLE-R> &i)>")
 qt_add_executable(myapp ${SOURCES})

The following example uses target_compile_definitions to set COMPILE_DEFINITIONS which will be added to OPTIONS.

 set(SOURCES myapp.cpp main.cpp)
 qt_wrap_cpp(SOURCES myapp.h
             TARGET myapp)
 qt_add_executable(myapp ${SOURCES})
 target_compile_definitions(myapp PRIVATE "$<$<CONFIG:Debug>:MY_OPTION_FOR_DEBUG>"
                                          "DEFINE_CMDLINE_SIGNAL=void cmdlineSignal(const QMap<int, int> &i)"
                                          "$<$<BOOL:TRUE>:DEFINE_CMDLINE_SIGNAL_IN_GENEX=void cmdlineSignal(const QMap<int$<COMMA> int$<ANGLE-R> &i)>")