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C++/WinRT implementation inheritance: Notes on winrt::implements, part 1

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Summary

  • winrt::implements is used for implementing interfaces in C++/WinRT.
  • The general pattern for winrt::implements is to repeat the name of the derived type as the first template parameter.
  • It uses the Curiously Recurring Template Pattern (CRTP) to access methods of the derived type.
  • The "other stuff" in winrt::implements can include C++/WinRT interfaces, classic COM interfaces, C++/WinRT runtime classes, marker classes, and other interfaces (maximum 1).
  • When implementing a C++/WinRT runtime class with multiple interfaces, only the first one is used, and the rest are ignored.
  • It's recommended to use the autogenerated T-template for implementing a runtime class declared in an IDL file instead of winrt::implements.

Bonus Chatter

  • Reading the C++/WinRT code and figuring it out can help you become an expert in implementing interfaces.
  • Understanding how winrt::implements works can help in better structuring code and ensuring that all required interfaces are implemented.