auto foo = ref new Foo(); What is "ref"?

Question

I was watching a video from, //build/ and several of the MS developers were using a syntax like this in their C++11 programs:

auto foo = ref new Foo();

I understand what everything does in this line except "ref". What does that mean?

Answer 1

The forthcoming Visual C++ compiler adds this syntax for dealing with WinRT objects (which are in turn the next generation of COM, what have we gone through now? COM, DCOM, COM+, ActiveX, ...)

That line is nearly equivalent to:

com_ptr_t<Foo> foo = CreateInstance<Foo>(); 

But there's a new version of com_ptr_t as well, using the syntax Foo^.

Answer 2

"ref new" is a 2 token keyword. It instructs the compiler to instantiate a windows runtime object and automatically manage the lifetime of the object (via the "^" operator).

Instantiating a windows runtime object causes an allocation, but it does not have to be on the heap.

Answer 3

ref in this case stands for reference counting. Classes using ref are WinRT component which have reference count machanisms out of the box.