QMetaObject

QMetaObject is a class in the Qt framework that stores the meta-information about a QObject-derived class. It is a core part of Qt's meta-object system (MOC), which enables runtime introspection, dynamic invocation, and the signal-slot mechanism. Each class declared with the Q_OBJECT macro has an associated QMetaObject that describes its name, inheritance, properties, signals, slots, and enumerations. An instance of a QObject can expose its meta-object at runtime through QObject::metaObject(), while a class type provides a static meta-object via ClassName::staticMetaObject.

The meta-object contains the class name and a reference to its superclass meta-object, as well as collections describing properties, methods (including signals and slots), and enumerations. This information allows code to inspect an object's capabilities, find properties by name, enumerate signals and slots, and query the signature of methods. The data is generated at build time by the Qt Meta-Object Compiler (moc).

Common uses include runtime introspection for debugging, implementing generic UI tooling, and supporting plugins where type information is discovered at runtime. It also enables dynamic method invocation through QMetaObject::invokeMethod and programmatic signal-slot connections in cases where static wiring is impractical.

Related types include QMetaMethod, QMetaProperty, and QMetaEnum, which represent individual members described by QMetaObject. A well-known limitation is that the meta-object data is only generated for classes that participate in the MOC system (typically QObject-derived classes with Q_OBJECT).