Thread overview
Transparent cast from class to member pointer?
Apr 14
diniz
Apr 15
diniz
Apr 15
Alex
April 14
struct IM;
struct C {
 IM *impl;
};

int cInit(C* self);

class I {
	C handler;

	this(){cInit(&handler);}
}

Is there a simple way that I can use handler without the address-of operator and automatically get *impl?

Something like:

class I {
	C handler;

	this(){cInit(handler);}
}

And later can use I in a way like this without having to define/write explicit casts everywhere?

someFunc(C* self);

I myI;
someFunc(myI);


-- 
Robert M. Münch
http://www.saphirion.com
smarter | better | faster

April 14
Le 14/04/2019 à 20:03, Robert M. Münch via Digitalmars-d-learn a écrit :
> struct IM;
> struct C {
>   IM *impl;
> };
> 
> int cInit(C* self);
> 
> class I {
>      C handler;
> 
>      this(){cInit(&handler);}
> }
> 
> Is there a simple way that I can use handler without the address-of operator and automatically get *impl?
> 
> Something like:
> 
> class I {
>      C handler;
> 
>      this(){cInit(handler);}
> }
> 
> And later can use I in a way like this without having to define/write explicit casts everywhere?
> 
> someFunc(C* self);
> 
> I myI;
> someFunc(myI);

Do you have a clear and correct view of what you want to express, of the application? How does it look (for us), if you replace IM, C, impl, cInit, I, handler, with meaningful (and correctly chosen) terms?

-- 
diniz {la vita e estranj}
April 15
On 2019-04-14 20:01:27 +0000, diniz said:

> Le 14/04/2019 à 20:03, Robert M. Münch via Digitalmars-d-learn a écrit :
>> struct IM;
>> struct C {
>>  IM *impl;
>> };
>> 
>> int cInit(C* self);
>> 
>> class I {
>>     C handler;
>> 
>>     this(){cInit(&handler);}
>> }
>> 
>> Is there a simple way that I can use handler without the address-of operator and automatically get *impl?
>> 
>> Something like:
>> 
>> class I {
>>     C handler;
>> 
>>     this(){cInit(handler);}
>> }
>> 
>> And later can use I in a way like this without having to define/write explicit casts everywhere?
>> 
>> someFunc(C* self);
>> 
>> I myI;
>> someFunc(myI);
> 
> Do you have a clear and correct view of what you want to express, of the application? How does it look (for us), if you replace IM, C, impl, cInit, I, handler, with meaningful (and correctly chosen) terms?

Well, ok... even it really doesn't matter a lot.

IM = Implementaiton Context (C-API)
C  = Core Context (C-API)
I  = Implementation D Class

The C side requires that *impl is the 1st member in the struct/class whereever it is stored. Hence, the wrapping in a struct and not directly putting it into a D class.

-- 
Robert M. Münch
http://www.saphirion.com
smarter | better | faster

April 15
On 04/14/2019 11:03 AM, Robert M. Münch wrote:
> struct IM;
> struct C {
>   IM *impl;
> };
> 
> int cInit(C* self);
> 
> class I {
>      C handler;
> 
>      this(){cInit(&handler);}
> }
> 
> Is there a simple way that I can use handler without the address-of operator and automatically get *impl?
> 
> Something like:
> 
> class I {
>      C handler;
> 
>      this(){cInit(handler);}
> }
> 
> And later can use I in a way like this without having to define/write explicit casts everywhere?
> 
> someFunc(C* self);
> 
> I myI;
> someFunc(myI);
> 
> 

'alias this' can do that:

struct IM;
struct C {
 IM *impl;
};

int cInit(C* self) {
  return 0;
}

class I {
    C handler;

    this(){cInit(&handler);}

  C* ptr() {               // <== ADDED
    return &handler;
  }

  alias ptr this;          // <== ADDED
}

void someFunc(C* self) {
}

void main() {
  I myI = new I();
  someFunc(myI);
}

Ali
April 15
Le 15/04/2019 à 08:30, Robert M. Münch via Digitalmars-d-learn a écrit :
> The C side requires that *impl is the 1st member in the struct/class whereever it is stored. Hence, the wrapping in a struct and not directly putting it into a D class.

All right! Did not think at this usage case, interfacing with C.

-- 
diniz {la vita e estranj}
April 15
On 2019-04-15 08:19:57 +0000, Ali ‡ehreli said:

> 'alias this' can do that:

Hi, I had the suspicion already...

> struct IM;
> struct C {
>   IM *impl;
> };
> 
> int cInit(C* self) {
>    return 0;
> }
> 
> class I {
>      C handler;
> 
>      this(){cInit(&handler);}
> 
>    C* ptr() {               // <== ADDED
>      return &handler;
>    }
> 
>    alias ptr this;          // <== ADDED
> }
> 
> void someFunc(C* self) {
> }
> 
> void main() {
>    I myI = new I();
>    someFunc(myI);
> }

Bingo, I didn't know that I can do an 'alias this' using a function and not only a type... pretty cool. So, with several of these I can setup implicit conversions to different types. Thanks.

-- 
Robert M. Münch
http://www.saphirion.com
smarter | better | faster

April 15
On Monday, 15 April 2019 at 15:07:10 UTC, Robert M. Münch wrote:
> On 2019-04-15 08:19:57 +0000, Ali ‡ehreli
>
> Bingo, I didn't know that I can do an 'alias this' using a function and not only a type... pretty cool. So, with several of these I can setup implicit conversions to different types. Thanks.

Well, as I know, multiple alias this won't work yet...
https://wiki.dlang.org/DIP66