When to use winrt::make vs constructors?

Question

These two code fragments seems to be having same affect

if (!m_mainWindow)
{
    m_mainWindow = winrt::make<App1::implementation::MainWindow>();
}

if (!m_mainWindow.Content())
{
    m_mainWindow.Content(winrt::make<App1::implementation::ShellPage>());
}
m_mainWindow.Activate();

---

if (!m_mainWindow)
{
    m_mainWindow = App1::MainWindow();
}

if (!m_mainWindow.Content())
{
    m_mainWindow.Content(App1::ShellPage());
}
m_mainWindow.Activate();

Is there a reason I should be using winrt::make instead of directly calling constructors. Microsoft docs seems to insists I should be using winrt::make, but why?

Answer 1

Those two code fragments are equivalent only if your projected opted into uniform construction, using cppwinrt's "-opt" flag as described here: https://learn.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/author-apis#opt-in-to-uniform-construction-and-direct-implementation-access

If you haven't opted in,the second code fragment will call RoGetActivationFactory to retrieve the factory and create an instance of the class, followed by ActivateInstance and QueryInterface, which is typically undesirable when you are dealing directly with that component's implementation. That page does a good job of explaining all the details.