inheriting constructos

[Michel Fortin]

On 2009-11-29 18:03:40 -0500, Andrei Alexandrescu 
<SeeWebsiteForEmail at erdani.org> said:

> Walter and I just discussed the matter of inheriting constructors. Our 
> thought on the issue:
> 
> a) If a class doesn't define any constructors and adds no fields, 
> inherit constructors. Example:
> 
> class MyException : Exception {}
> 
> b) If a class defines at least one constructor, do not inherit constructors.
> 
> c) If a class doesn't define any constructors but does add at least a 
> non-static field -> undecided.
> 
> What do you think?

Objective-C has 'a' and 'c' acting like 'a'. There's no 'b' though, and 
this is a small annoyance, as "constructors" in Objective-C are just 
normal methods with a name that starts with "init".

Personally, I'd say adding a field to a class shouldn't affect its 
constructor. If you need to initialize the field at object's 
construction, then you add a constructor. But otherwise, if you don't 
need to initialize it at construction (which happens fairly often when 
fields are zeroed anyway), then you can certainly inherit super's 
constructors.

In fact, I find it hard to see a justification for making adding a 
field break constructor inheritance. My experience with Objective-C 
tells me that 'c' acting like 'a' wouldn't be a problem at all because 
D, just like Objective-C, initializes all fields to a default value 
anyway. You only need a constructor when you want a non-default value 
in a field.

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/