Why Do I Get a \'vtable Reference Error\' with Q_OBJECT in Qt?

vtable Reference Error with Q_OBJECT in Qt

In this instance, the linker is unable to locate the virtual function table (vtable) for the T class, resulting in the error "undefined reference to `vtable for T'". This issue arises when the MOC-generated unit, responsible for managing Qt's meta-object system, is excluded from the linking process.

To address this, consider the following:

• Separate Header File: Define the T class in a separate header file. This ensures that the build system scans the header file during compilation.
• Updated qmake: If the class was previously not part of the meta-object system, re-run qmake by modifying the timestamp of the project file (e.g., adding and removing whitespace) to force its execution.
• Qt Creator Integration: In Qt Creator, selecting "Run qmake" from the project context menu triggers qmake execution.

Once these steps are taken, the MOC unit will be included in the linking process, resolving the vtable reference error.

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