Question

I’m coming from C# background, learning C++, specifically on the Windows Phone 8 platform.

Many code samples (installed with the SDK) show usage of the Hat operator ^ (Reference here: Types that wear hats).

For example:

void PhoneDX::Initialize(CoreApplicationView^ applicationView)
{
    // ... function body
}

I am wondering:

• Why are most of the pointers being defined in that manner, specifically on Windows Phone 8 ?

• Is that syntax mandatory? Suppose i am using a C++ native library from another platform (that doesn’t use this syntax). Should it work with no issues?

Answer 1

A hat is a compiler-supported smart pointer type that is designed to make Windows Runtime types easier to work with from C++ code. As discussed in “Types That Wear Hats” and the other articles in that series, the C++/CX language extensions are optional: any code that can be written using C++/CX can be written in C++ without using the language extensions, albeit at greater code complexity and verbosity.

The key here is that hats are designed to facilitate code that makes use of Windows Runtime types. In general, you should confine your use of C++/CX and Windows Runtime types to the boundary of your components: most of your code should be standard, portable, normal C++ code. C++/CX should be used (1) to wrap C++ code to make it consumable through the Windows Runtime and (2) to use other Windows Runtime components from your component.

So, yes, the syntax is optional, but you should strongly consider using it when writing code that must work with Windows Runtime types. You should be able to use any ordinary C++ code, without modification, with the caveat that Windows Store apps and Windows Phone apps run with low privileges and some facilities are not available (e.g., there is no console, so console I/O doesn’t work, and the runtime provides specialized process lifetime management facilities, so calling exit is a bad idea).