Re: [boost] Re: [gui] The Big Picture

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-12-30 19:48:02

Mathew Robertson wrote:
>>>> Yeah, geez.  Single-rooted hierarchies of diverse functionality
>>>> with a root class called "object" were discredited long ago,
>>>> weren't they?
>>>
>>> I am not suggesting a single-rooted heirarchy for *all* the classes
>>> as that would be stupid. MFC does it to support their own version
>>> of RTTI, memory leak tracking, etc. Java does it because it doesn't
>>> have templates. .NET has it because it treats every object as a COM
>>> object.
>>
>> Python does it too.  It's not neccessarily wrong for other languages;
>> just C++.
>
> hmm.... If C++ had implemented an 'Object' back in 1980, then "single
> rooted heirachy"s wouldn't be questioned...

We'd still be using C in that case. ;-)

Bad single-rooted hierarchies are bad in principle; it doesn't depend on 
language. The problem occurs when the base class acquires functionality that 
90% of the descendants have. The other 10% are forced to implement something 
that they do not support. Over time, this can lead to "spectacular" designs.

All of the above examples do not fit this description; the root "object" is 
simply what constitutes an object in that particular language. Since in C++ 
everything can be an object, the root class is "void".