Initializing a class pointer

[Tyro[a.c.edwards]]

On 2/27/2011 8:52 AM, Simen kjaeraas wrote:
> Tyro[a.c.edwards] <nospam at home.com> wrote:
>
>> I'm trying to convert some c++ code that defines
>>
>> T func(par...)
>> {
>> Controller * pCtrl = WinGetLong<Controller *> (hwnd);
>> .
>> .
>> .
>> switch(msg)
>> {
>> case FirstMatch:
>> pCtrl = new Controller (hwnd, reinterpret_cast<CREATESTRUCT *> (lParam));
>> break;
>> }
>> }
>>
>> I'm not sure why I need a pointer to the class, just trying to figure
>> it out.
>
> Ah. You would not need a pointer to the class in D. Instead, your function
> would look something like this:
>
> T funct(par...)
> {
> auto pCtrl = WinGetLong!Controller(hwnd);
> ...
> switch(msg)
> {
> case FirstMatch:
> pCtrl = new Controller(hWnd, cast(CREATESTRUCT*)lParam);
> break;
> }
> }
>
> C++ classes are in some ways more akin to D structs, in that:
>
> class A {};
>
> void foo(){
> A bar;
> }
>
> bar would be allocated on the stack in C++, while in D bar would be a
> pointer to a class instance on the heap. (well, it would be null, but
> when you set it to something, that something would reside on the heap)
>

Ok, that's essentially what I have, except that I used Controller pCtrl 
vice auto. WinGetLong however, is a template that calls 
GetWindowLongPtrA() and casts it's result (in this case) to Controller. 
  GetWindowLongPtrA() returns LONG_PTR (aka int) and therefore fails 
miserably on the cast attempt. On the reverse, there is a WinSetLong 
that attempts to cast Controller to int for use with 
SetWindowLongPtrA(). Neither of these functions complain when I use 
Controller* but I end up with the problem of trying to initialize a 
pointer with a reference to Controller.