[squeak-dev] Re: On traits composition
andreas.raab at gmx.de
Tue Dec 8 20:37:28 UTC 2009
Eliot Miranda wrote:
> but as an error. There isn't any way of removing a method. Were foo
> inherited from some superclass then unless the error method is generated
> there would be no indication that there was a conflict between the two
> traits defining foo. So traitError is a more specific version of
> self shouldNotImplement
> is not as descriptive (it could be expressing the class author's intent) as
> self traitConflict
> but both are equivalent; they raise run-time errors saying "this method
> shouldn't be here". That's not the same as saying the conflict shows up
> as a useful method; it doesn't.
My understanding was that #traitConflict is essentially equivalent to a
"self shouldBeImplemented", i.e., an indicator that manual work is
needed to resolve the conflict. That's why I'm saying that "last one
wins" would be a useful default more often than raising an error. See my
previous comment - the idea that traits are (by design) intended to
represent an XOR of methods is complete news to me. It'd be good if
someone could back this up.
BTW, I really don't think there is much difference between mixins and
traits; all forms of MI are fairly equivalent.
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