Hi, could someone tell me why this code gives an access violation? It seems I must be missing some fundamental difference between C++ and D.

class C
{
    void zing() {}
}

void main()
{
    C c;
    c.zing();
}

Robin Allen wrote:

> Hi, could someone tell me why this code gives an access violation? It seems I must be missing some fundamental difference between C++ and D.
> 
> class C
> {
>     void zing() {}
> }
> 
> void main()
> {
>     C c;
>     c.zing();
> }

Yes :)

classes are reference types so the current value of c is null. To initialize c change "C c;" into "C c=new C()".

Robin Allen wrote:
> Hi, could someone tell me why this code gives an access violation? It seems I
> must be missing some fundamental difference between C++ and D.
> 
> class C
> {
>     void zing() {}
> }
> 
> void main()
> {
>     C c;
>     c.zing();
> }

Using objects in D is similar to using them in Java in that objects are reference-based.  Try:

    void main()
    {
        // Will be collected by the GC at some point after c goes
        // out of scope.
        C c = new C();
        c.zing();

        // Will be destroyed automatically the moment d goes out of
        // scope.  The class instance may be allocated on the stack
        // but is not required to be.
        scope C d = new C();
        d.zing();
    }


Sean

Ah, so you only ever work with references, and you always use new. Thanks to both of you.

Robin Allen wrote:
> Ah, so you only ever work with references, and you always use new. Thanks to both
> of you.

When dealing with classes, yes. But not with structs, which are value types. So this:

MyStruct c;
c.someFunc();

actually works, since struct instances are not references.