On Fri, 11 Feb 2011, Stéphane Rollandin wrote:

>>  I think #is: is a terrible idea
>
> A possible solution is to name it #isA: and limit its semantics to 
> inheritance testing only. We discussed this at length one year ago in that 
> thread:

If you would only use it for inheritance testing, then why bother with it 
at all? #isKindOf: is already in the image and does exactly that.

In general #is: works as long as you don't have to add a protocol to a 
class that already implements #is:.


Levente

>
> http://forum.world.st/Object-gt-gt-is-was-Re-PackageDependencyTest-td1578541.html
> (and following pages)
>
>
>
> The reason I thought (and still think) Object>>#is: is a bad design for 
> protocol implementation can be summarized by the following citations of mine 
> (see the thread for more context):
>
> ----
>
> all #is:-type of attributes have to be centralized in
> one place, the #is: method.
>
> a Morph that isMorph, isBeautiful and isWhatMyUncleLikes has to provide
> the three answers to very different questions in the same place. Now if
> another package needs to know if a Morph isMyCupOfTea, it must override
> aMorph>>#is:
>
> so #is: can not actually safely belong to a single package. while
> #isWhatMyUncleLikes will only be in my package MyUncle, except if
> someone else has the same kind of weird ideas about protocol names.
>
> plus, looking for the senders of #isBeautiful immediately gives me all
> classes responding to the protocol. with the #is: idea, all protocols
> are mangled in one: you have to look at all #is: implementations, in all
> objects (!) to see where you protocol went.
>
> ----
>
> #is: becomes an attractor, a fixed point for all protocols, dispatched
> on all classes and having to support all packages. it's another form of
> the God class: it's the God method for protocols. this is not OOP as I
> understand (and practice) it.
>
> ----
>
>
>
> I was answered by proponents of Object>>#is: that my points were moot because 
> extension methods were evil and I was doing monkey patching. So in the end we 
> talked about what is good practice in that matter, and disagreed :)
>
>
>
> Stef
>
>