Re: Total Newbie Backward Compat Question

Chris ( Val ) wrote:

> On Mar 11, 1:21 am, Richard Heathfield <r...@[EMAIL PROTECTED]
> wrote:
>> Chris ( Val ) said:
>>
>> <snip>
>>
>> > Why did you write setters that return values?
>>
>> int oldx = p.setx(newx);
>> dosomethingwith(p);
>> p.setx(oldx);
>>
>> is quite a useful thing to be able to do. You can get the same deal
>> with:
> 
> I think I can understand your reasons for it, but that is a hack in
> C++, and goes against everything we learn about OOP and writing good,
> maintainable and safe code.

I am sorry, but I don't see how you come to that conclusion.
I would regard such a setter that returns the previous value as
perfectly valid OOP, if two conditions are met:
1. Having the setter at all does not blatantly violate the principles of
OOD.
2. This return value is not the sole means of retrieving the current
value.

For Richard's example, the second condition is definitely matched and
the first might be debatable if we knew more about the context in which
the point class will be used. For now, I would just accept it.

> 
> Some setters are written to return a 'boolean' value to signal either
> success or failure, but even that is debatable in some cir***stances,
> when compared to throwing an exception.

If it is actually a setter, and not a function that happens to set some
values as part of a larger operation, then I would strongly prefer a
return value over an exception to indicate failure, unless there is
reason to believe that the immediate caller will not be able to handle
the problem.

Bart v Ingen Schenau
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