Suggestion: common & polish constructors (+ destructors)

[Kristian Kilpi]

On Fri, 03 Nov 2006 18:01:16 +0200, Georg Wrede <georg.wrede at nospam.org>  
wrote:

> Kristian Kilpi wrote:
>> On Fri, 03 Nov 2006 14:33:20 +0200, Bill Baxter <wbaxter at gmail.com>  
>> wrote:
>>
>>> Kristian Kilpi wrote:
>>>
>>>>  It would be nice if you could add code into constructors (and   
>>>> destructors)  with mixins. For example, you could initialize member   
>>>> objects/structures  added by a mixin, etc.
>>>> [snip]
>>>> And finally, there should also be common destructors (e.g.    
>>>> '~common_this()', 'finish_this()', 'destroy_this()') to be used  
>>>> with   mixins. This way each mixin could add code to the actual  
>>>> destructor.
>>>
>>>
>>> Actually what you suggest seems to already be the case for  
>>> destructors.    Don't know if it's in the spec, but I just noticed it  
>>> yesterday.
>>>
>>>
>>> template Death(int i)
>>> {
>>>      ~this() {
>>>          writefln("Death says: see you! ", i);
>>>      }
>>> }
>>> class DClass
>>> {
>>>      mixin Death!(1);
>>>      mixin Death!(2);
>>>      mixin Death!(3);
>>>
>>>      ~this() {
>>>          writefln("Class bye bye!");
>>>      }
>>>
>>>      mixin Death!(4);
>>>      mixin Death!(5);
>>>      mixin Death!(6);
>>> }
>>>
>>> The destructors get called in reverse order of appearance within  
>>> DClass.
>>>
>>> --bb
>>   Well now, that's nice. :)
>>  This feature is not yet documented, maybe Walter is experimenting  
>> things  for future releases... Hopefully we'll have something like it  
>> for the  ctors also.
>
> I wonder if this is an accidental artifact of compiler internals?
>
> I don't remember seeing any justifications for this behavior.

If it is a bug, then it's a useful one.

Several times in my C++ projects I have used macros to add methods etc to  
classes and code to constructors (and that's even if objects are value  
types and structures have ctors etc in C++). It's a very annoying -- and  
potentially buggish -- way. An alternate way would be to write/copy the  
same code over and over again, but it's more error-prone, of course.