Re: [boost] [pimpl] Proposal. Determining interest.

From: Michael Marcin (mmarcin_at_[hidden])
Date: 2007-11-03 18:13:45

Vladimir Batov wrote:
> Marc,
> 
> Just uploaded v0.6 which supports building of two separate class 
> hierarchies -- separately for interfaces and for implementations as 
> described in GoF Pattern Bible for the Bridge pattern.
> 
> The interface hierarchy is built as
> 
> struct Base : public pimpl<Base>::pointer_semantics {...};
> 
> struct Derived : public Base {...}
> 
>  etc.
> 
> The implementation hierarchy is still hidden and is built as
> 
> template<> struct pimpl<Base>::implementation {...};
> 
> template<> struct pimpl<Derived>::implementation : public 
> pimpl<Base>::implementation {...};
> 
> etc.
> 
> Marc, let me know if that looks right for your purpose as I myself have no 
> use for deep inheritance trees to test them out.
> 
> Best,
> Vladimir.
> 
>> Marc,
>>
>> I have re-read the Bridge pattern in GoF Pattern Bible. Their example is
>> just what you describe in your example. I agree that having/supporting
>> two separate hierarchies is an elegant solution to a few problems. Let
>> me think how pimpl<> might support that.
>>

Out of curiosity in this and all other examples of this pimpl library 
public inheritance is used. Isn't this an implemented in terms (spelled 
private) of rather than an IS-A (spelled public) relationship?

I'm sure there is a technical reason I'm missing.

Thanks,

Michael Marcin