Reference to D class instance with a C library

[Adam D. Ruppe]

On Saturday, 13 July 2013 at 18:30:24 UTC, Leandro Motta Barros 
wrote:
> So, is there some way to store a reference to a D class 
> instance in that 'user_data' field?

Should be ok to cast the reference itself to that type - don't 
take the address of it, since that would be the address of a 
local, but just cast it:

MyObject foo = new MyObject();

c_struct.user_data = cast(intptr_t) foo;

And when you get it back:

foo = cast(MyObject) c_struct.user_data;


In D, MyObject is already basically a MyObject*, so if you did 
&foo, the type would be more like MyObject** which is probably 
why you didn't have luck doing it before.