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main.cpp
main.cpp
 
 
singletoninstance.cpp
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README.md

QML5 Singleton Instance - Exporting a C++ singleton to QML

This is a minimal example to learn how to use qmlRegisterSingletonInstance().

This project uses the new CMake API for Qt6.

Use a singleton when you need globally accessible data with a type you do not need to explicitly instantiate.

  • Prefer the new QML_SINGLETON method over this.
  • Prefer this over setContextProperty().
  • Q_INVOKABLE or slots apply here.
  • Imports are mandatory. This allows to import only where necessary.
  • Singletons made this way require a static factory function.
  • When:
    • The static function is in-class, it is possible to hide the constructor, so it can be made to be a true C++ singleton, in addition to a QML one.
    • The static function is out-of-class, it is not possible to hide the constructor, so it is not a true C++ singleton, just a QML one.