Object as function argument

[Chris Sperandio via Digitalmars-d-learn]

Hi,

I'm a developer coming from C and I've a question about class 
instance as method or function parameter.
In the book "The D Programming Language", I read the instance was 
passed by reference to functions (in the opposite of structures). 
I understood that it was the same object in the function and the 
caller. But I'm think, I was wrong because when I print the 
addresses of an object before the function call and inside the 
function, they're not the same but the changes from the function 
are kept in the instance.
If I use the "ref" qualifier in the function declaration, the 2 
addresses are the same.

How do the changes work in the function? Is there a copy ? Or a 
"magic" trick :) ?

Chris