[squeak-dev] #shouldBeImplemented vs #notYetImplemented

Thiede, Christoph Christoph.Thiede at student.hpi.uni-potsdam.de
Sat Jan 25 13:21:15 UTC 2020

Thanks Bert, but then, what is the difference between #shouldBeImplemented and #subclassResponsibility?

And if I understand you correctly, the method stub created by a debugger should rather insert a #notYetImplemented than a #shouldBeImplemented, shouldn't it?


Von: Squeak-dev <squeak-dev-bounces at lists.squeakfoundation.org> im Auftrag von Bert Freudenberg <bert at freudenbergs.de>
Gesendet: Samstag, 25. Januar 2020 01:13:10
An: The general-purpose Squeak developers list
Betreff: Re: [squeak-dev] #shouldBeImplemented vs #notYetImplemented

If a class has a method sending #shouldBeImplemented, then subclasses are supposed to override that method, without modifying the superclass method. It basically marks that class as abstract.

In contrast, #notYetImplemented indicates that the method itself should be modified, replacing the #notYetImplemented send with the actual code.

- Bert -

On Fri, Jan 24, 2020 at 7:10 AM Thiede, Christoph <Christoph.Thiede at student.hpi.uni-potsdam.de<mailto:Christoph.Thiede at student.hpi.uni-potsdam.de>> wrote:

Hi all,

what exactly is the intended difference between #shouldBeImplemented and #notYetImplemented? It feels a bit confusing.

I have always used #shouldBeImplemented only because it is predefined by the Debugger.

But today I met #notYetImplemented and now wonder which one I should use:

  *   Both are detected by the debugger
  *   But #notYetImplemented has its own subclass implementation of NotImplemented which handles #receiverClass and #selector. I like this, it has a bit more object-orientation appeal.
  *   The names don't give me an indication to any semantical difference
  *   They are not in the same message category of Object at all!
  *   #shouldBeImplemented raises a specific error message, while that one of #notYetImplemented is generic and less precise
  *   But why does the #shouldBeImpleemented message mention "or a superclass should implement"? Given the subclass Bar of the superclass Foo and I compile '#baz ^self shouldBeImplemented' on Bar. Why should this indicate that #baz might have to implemented on Foo instead?
  *   Btw, we also have Object >> #required, which looks more Trait specific. Is it a problem that Tools-Debugger depends on Traits via this selector?

However, I think we might have some heterogenic duplication here, or at least miss any documentation of the differences. Can you tell me more about the history of both selectors? Should we try to merge them?


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