D Classes Passed By Reference or Value?

[Alex Parrill via Digitalmars-d-learn]

On Sunday, 16 August 2015 at 22:31:02 UTC, Brandon Ragland wrote:
> Hi All, I'm a bit confused as to how Classes in D are passed in 
> arguments and returns.
>
> Take this for example:
>
> class MyClass{
> int x = 2;
> }
>
> And then in app.d
>
> ref MyClass doStuff(){
> MyClass mc = new MyClass() // Heap allocation, using new....
> return mc;
> }
>
> The above fails, as "escaping reference to local variable" 
> however, this was created using new.... Not understanding what 
> the deal is, this should be a valid heap allocated object, and 
> therefore, why can I not pass this by reference? I don't want 
> this to be a local variable...
>
> So this begs the question: Are Classes (Objects) passed by 
> reference already?
>
> -Brandon

Classes are reference types, a la Java/C#.

     class MyClass {
         int x = 5;
     }

     void main() {
         auto c1 = new MyClass();
         auto c2 = c1;
         c1.x = 123;
         assert(c2.x == 123);
     }