[squeak-dev] Re: Object>>#is:? (was: Re: PackageDependencyTest)
juan at jvuletich.org
Thu Mar 4 20:33:57 UTC 2010
Andreas Raab wrote:
> For discussion, this is what I'm suggesting:
> Object>>is: aSymbol
> "A generic membership test. Should be used to avoid the
> proliferation of isXXX
> methods where appropriate. Use it like here:
> FooBar>>is: aSymbol
> ^aSymbol == #Foo or:[aSymbol == #Bar or:[super is: aSymbol]]
> This implementation can also be used with class names to replace
> the usage
> of aMorph isKindOf: SketchEditorMorph with, e.g., aMorph is:
> to avoid unnecessary dependencies on classes"
> "Check to see if aSymbol is a class name in the receiver's
> self class environment
> at: aSymbol
> ifPresent:[:aClass| ^self isKindOf: aClass].
I believe #isKindOf: is really bad. Reasons for this are given in
http://userweb.cs.utexas.edu/~wcook/Drafts/2009/essay.pdf . This was
also discussed here, you can google for the name of the pdf in the archives.
In the Cuis implementation of Object>>#is: there is no call to
#isKindOf:. The idea is to ask for a protocol, not for inheritance.
More information about the Squeak-dev