1. Qt Meta Object System

The Meta-Object Compiler, moc, is the program that handles. The moc tool reads a C header file. If it finds one or more class declarations that contain the macro, it produces a C source file containing the meta-object code for those classes. Among other things, meta-object code is required for the signals and slots mechanism, the run-time type information, and the dynamic property system. The C source file generated by moc must be compiled and linked with the implementation of the class.

If you use to create your makefiles, build rules will be included that call the moc when required, so you will not need to use the moc directly. For more background information on moc, see Usage moc is typically used with an input file containing class declarations like this. Mocfoo.cpp: foo.h moc $(DEFINES) $(INCPATH) $. Option Description -o Write output to rather than to standard output.f Force the generation of an #include statement in the output. This is the default for header files whose extension starts with H or h. This option is useful if you have header files that do not follow the standard naming conventions.

The part is optional.i Do not generate an #include statement in the output. This may be used to run the moc on on a C file containing one or more class declarations.

You should then #include the meta-object code in the.cpp file.nw Do not generate any warnings. (Not recommended.) -p Makes the moc prepend / to the file name in the generated #include statement.I Add dir to the include path for header files.E Preprocess only; do not generate meta-object code.D= Define macro, with optional definition.U Undefine macro.M Append additional meta data to plugins. If a class has specified, the key-value pair will be added to its meta data. This will end up in the Json object that gets resolved for the plugin at run time (accessible from ). This argument is typically used for tagging static plugins with information resolved by the build system.

@ Read additional command-line options from. Each line of the file is treated as a single option. Empty lines are ignored. Note that this option is not supported within the options file itself (i.e. An options file can't 'include' another file).h Display the usage and the list of options.v Display moc's version number.

Add the framework directory dir to the head of the list of directories to be searched for header files. These directories are interleaved with those specified by -I options and are scanned in a left-to-right order (see the manpage for gcc). Normally, use -F /Library/Frameworks/ You can explicitly tell the moc not to parse parts of a header file. Moc defines the preprocessor symbol QMOCRUN. Any code surrounded.

Qt Meta Object System

#ifndef QMOCRUN. #endif is skipped by the moc. Diagnostics moc will warn you about a number of dangerous or illegal constructs in the class declarations. If you get linkage errors in the final building phase of your program, saying that YourClass::className is undefined or that YourClass lacks a vtable, something has been done wrong. Most often, you have forgotten to compile or #include the moc-generated C code, or (in the former case) include that object file in the link command. If you use qmake, try rerunning it to update your makefile. This should do the trick.

Limitations moc does not handle all of C. The main problem is that class templates cannot have the macro. Here is an example.