class problems

[Timothy V]

Hi,
I'm having trouble figuring out something. How do i pass a class instance to
a function without 'creating a copy'. In C/C++ i would use &. For example
(C/C++):
class CLASS;
void function(CLASS &c);

Would someone be able to explain this?

Thank you very much in advance,

Timothy.

 

[John Baro]

IIRC this passes the ref of the existing instance?
You want to pass by ref in this case which will pass the actual reference
instead of a new reference pointing to the same object.

To clarify
void FunctionX(MyCustomClass MyCustomInstance)
Calls to FunctionX will create a new ref on the stack pointing to
MyCustomInstance.
This does not create a new instance of MyCustomClass, rather a new pointer
to the existing instance.

In this case if we set MyCustomInstance to null, the callee will still have
a valid ref to the instance.

If we change it to
void FunctionX(MyCustomClass ref MyCustomInstance)
Then calls to FunctionX will pass the existing ref on the stack and not
create a new one.

In this case if we set MyCustomInstance to null, the callee will not have a
valid ref to the instance any more.

Have a read of Jon Skeet's site, he has an excellent FAQ re this sort of
thing.
Address is
http://www.pobox.com/~skeet


Cheers
JB