Here are a few question-based titles that capture the core issue and solution from your article: * Undefined Reference to Vtable in Qt - Why and How to Fix It? * Qt: QObject and QGraphicsItem Inher

Undefined Reference to Vtable for T: Q_OBJECT Issue

In Qt development, attempting to inherit multiple base classes, notably QObject and QGraphicsItem, while utilizing signals and slots may result in enigmatic linker errors related to undefined references to vtables. These errors arise primarily because the appropriate MOC (Meta-Object Compiler) unit isn't included in the linking process, or its generation faces impediments.

To resolve this issue, consider the following steps:

• Segregate Header Files: Move the class declaration into a distinct header file. This ensures the build system can effectively scan implementation files.
• Force qmake Invocation: Trigger qmake's execution by making small modifications to the project file (such as introducing and then eliminating whitespace characters). This forces qmake to regenerate necessary rules, particularly for MOC.
• Project Context Menu (Qt Creator): If using Qt Creator, execute "Run qmake" from the project's context menu to explicitly trigger qmake.

Implementing these measures should eliminate undefined vtable references and allow for seamless compilation of your Qt code.

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