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c++-winrt

cppwinrt A subclass of Panel (or other class)，What constructors are needed？

I'm sorry my English isn't very good. I have a class like this

   struct WrapPanel :winrt::Windows::UI::Xaml::Controls::PanelT<WrapPanel>
   {
   public:
       WrapPanel(std::nullptr_t) {};
       // other code.....
   }

Use in other classes 

    WrapPanel wrapPanel{ ItemsPanelRoot().try_as<WrapPanel>()};
    //Error C2440   'initializing': cannot convert from 'initializer list' to 'WrapPanel'

like： https://learn.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/move-to-winrt-from-cx Converting from a base runtime class to a derived one

Solution

  • If you author a runtime class in C++/WinRT, you'll get several classes with the same name in different namespaces. Let's suppose that there's a namespace named NS1, in which there's a runtime class called WrapPanel, you'll get winrt::NS1::WrapPanel, winrt::NS1::implementation::WrapPanel and winrt::NS1::factory_implementation::WrapPanel. The first one is the "projection" of the runtime class, which we usually use; the second one is the "implementation", which implements the runtime class; the third one is the "factory", which is used by module.g.cpp.

    If you convert a base class to a derived one, you should use the "projection". It seems that you have used the "implementation".