Why does qmake/moc only process header files?

[doberkofler]

I was wondering, why qmake/moc only processes header (*.h) files and not source (*.cpp) files?
I just wonted to declare a class locally in a source module and discovered, that no moc files have been generated.
Why this restriction and how should it be worked around?
Thank you,
Dieter

[pitonyak]

It only looks at *.h files because that is where classes are usually defined. The work around is to define your "private" class in a .h file.

[squidge]

If you want a private class that is local to a file, then create a private header file only included by that source file. For example, myfile_internal.h and define your classes there.

[wysota]

There is a better way. If your implementation file that contains a local class is called xyz.cpp then write this under the class declaration:

#include "xyz.moc"

#include "xyz.moc"

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This instructs qmake to force running moc on xyz.cpp. Remember to rerun qmake after you add this statement.

class MyLocalClass : public QObject {
  Q_OBJECT
public:
// ...
};
 
#include "myfile.moc"

class MyLocalClass : public QObject {
  Q_OBJECT
public:
// ...
};

#include "myfile.moc"

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[doberkofler]

I'm not sure if I understand you correctly. Does the include xyz.moc have to to exist and what should it contain?

[squidge]

I believe the only reason it is there is that when the makefile is rebuilt it will automatically create a rule to parse the cpp file using MOC, as qmake will parse cpp files for #include lines for dependancy purposes.

Some people also state that doing so can reduce compilation time: http://edu.kde.org/development/tips....emyfilemoccode
There some discussion about it on the Qt interest archive: http://lists.trolltech.com/qt-intere...ad00793-0.html
And it seems to be used more in KDE: http://www.kdevelop.org/3.0/doc/tutorial_settings/#p1

[wysota]

For me it's just a matter of convinience that I don't have to create separate header files just to declare local classes.