Question

UPDATE So totally pulled a tool moment. I really meant by reference versus Out/Ref. Anything that says ‘ref’ I really meant by reference as in

SomeMethod(Object someObject)

Versus

SomeMethod(out someObject)

Sorry. Just don’t want to change the code so the answers already make sense.

Far as I understand, unlike ref where it ‘copies’ the pointer and creates a new space on the stack to use that pointer, but won’t change the pointer:

SomeMethod() {  SomeThing outer = new SomeThing();  RefMethod(ref outer) }  RefMethod(ref inner)  //new space on stack created and uses same pointer as outer {    inner.Hi = 'There'; //updated the object being pointed to by outer    inner = new SomeThing();//Given a new pointer, no longer shares pointer with outer                            //New object on the heap } 

Out copies the pointer and can manipulate where it points to:

SomeMethod() {  SomeThing outer = new SomeThing();  RefMethod(out outer) }  RefMethod(out inner)  //same pointer shared {     inner = new SomeThing();//pointer now points to new place on heap                              //outer now points to new object                            //Old object is orphaned if nothing else points to it } 

That’s fine and dandy with objects, but what about value types seeing as they have nothing to point to being only on the stack?

Answer 1

Just because the variable lives on the stack (if it’s a local variable) doesn’t mean you can’t create a pointer to it – and indeed that’s the case with reference types as well.

The pointer within RefMethod is to the ‘outer’ variable – and the variable itself lives on the stack as it’s an uncaptured local variable.

As Leppie said, ref and out are identical except for the rules on definite assignment – in fact, the only difference in IL is an attribute applied to out parameters.

See my article on parameter passing for more details about ref/out in general.