c++ winrt uwp 如何从依赖属性中获取值

Question

Given a dependency property in a Custom attached property defined in it's class as

   private:
            static Windows::UI::Xaml::DependencyProperty m_IsOpenProperty;

I have tried,

bool FlyoutCloser::GetIsOpen(Windows::UI::Xaml::DependencyObject const& target)
    {
        return target.GetValue(m_IsOpenProperty).as<bool>();

    }

however here the compiler is telling me C++ no suitable conversion function from to exists converting from winrt::impl::com_ref<bool> to "bool" exists. How can I get a boolean value out of it.

Answer 1

target.GetValue() will return an IInspectable type, you need to use winrt::unbox_value function to unbox an IInspectable back into a scalar value instead of using as method. And about boxing and unboxing, you can refer to this document .

bool FlyoutCloser::GetIsOpen(Windows::UI::Xaml::DependencyObject const& target)
{
    return winrt::unbox_value<bool>(target.GetValue(m_IsOpenProperty));
}

void FlyoutCloser::SetIsOpen(Windows::UI::Xaml::DependencyObject const& target, bool value)
{
    target.SetValue(m_IsOpenProperty, winrt::box_value(value));
}