"operator" overloading?

[Simon]

On 23/02/2011 14:37, Dmitry Olshansky wrote:
> On 23.02.2011 17:08, %u wrote:
>> Hi everyone,
>>
>> Was hoping someone could help me make sense of this bit of C++ code:
>>
>> class canvas
>> {
>> operator HDC() { return _hdc; }
>> protected:
>> canvas(HDC hdc): _hdc(hdc) {}
>> HDC _hdc;
>> }
>>
>> From what I understand, HDC is an alias for HANDLE in Windows. So
>> they are overloading canvas such that when assigned to handle
>> instance it returns _hdc? How is this done in D?
>>
>> Thanks
>
> Something like this, and i shouldn't be a class in D (it's a proxy sort
> of, right? ) :
>
> struct canvas{
> alias getHandle this;
> this(HDC hdc){
> _hdc = hdc;
> }
> @property HDC getHandle(){ return _hdc; }
> private:
> HDC _hdc;
> }
>
> uinttest{
> HDC h = cast(HDC)1;
> canvas c = h;//intitalize
> h = c;
> assert(h == c);
> }
>

That's the wrong way round.

The c++ class is a canvas object which can be transparently passed to 
any windows function which takes a HDC.

Note the constructor is protected and the cast operator is public.

Not sure of the cast operator details in D though; I've never used it 
myself.

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