Taking a copy of an object

[Bruno Medeiros]

kris wrote:
> Bruno Medeiros wrote:
>> kris wrote:
>>
>>>
>>> BTW: one concern I'd have with a root-Object dup() method is the need 
>>> to cast the returned instance. Presumeably a more specific compiler 
>>> implementation (of object.dup) would sidestep that need for casting?
>>
>>
>> There is no need for casting. Since D supports covariant return types, 
>> the overriding methods can return their specific types:
>>
>>   class Foo {
>>     Foo Clone() {
>>       return new Foo();
>>     }
>>   }
>>
>>   class FooBar : Foo {
>>     override FooBar Clone() {
>>       return new FooBar();
>>     }
>>   }
>>
> 
> 
> Yes, we're well aware of the covariance aspect. However, we'd been 
> talking about /one/ method to handle all shallow class copy (perhaps in 
> the root Object, as was noted). Why one method? So (a) you don't have to 
> add the above to each and every class that might possibly be copied at 
> some point in the future, and (b) you don't end up being confused when 
> you dup a class and wind-up with a partial copy (and a cast requirement) 
> when a superclass method is invoked instead.
> 
> Covariance is all well and good, but we stepped beyond that point early 
> on. Perhaps you'll re-read the first paragraph again and understand it 
> better?
> 
> 

Hum, you're right, I thought you were talking about deep copy.

-- 
Bruno Medeiros - MSc in CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D