[Newbies] AbstractObjectsAsMethod

[stes@PANDORA.BE]

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It seems the runtime (VM) defines a special selector

#define SelectorRunWithIn 49

for a message  with:run:in:  

I don't know the details of the purpose of this selector,
but I think the VM supports it so that subclasses of AbstractObjectsAsMethod,
not just subclasses of CompiledMethod, can be used as methods.

As a test (this could be documented somewhere, for example on wiki.squeak.org)
consider 2 classes 'Foo' and 'Bar' :
  
AbstractObjectsAsMethod subclass: #Foo
        instanceVariableNames: ''
        classVariableNames: ''
        poolDictionaries: ''
        category: 'ObjectAsMethodTrivial'!

!Foo methodsFor: 'RuntimeSupport'!
run:aSelector with:arguments in:aReceiver
	""
	Transcript show:'in Foo run:with:in:'.
	Transcript cr.
	^ self! !

Object subclass: #Bar
        instanceVariableNames: ''
        classVariableNames: ''
        poolDictionaries: ''
        category: 'ObjectAsMethodTrivial'!

!Bar class methodsFor: 'class initialization'!
addFooBar
	""
	self addSelector:#foobar withMethod:(Foo new).
	^ self! !

Now after fileIn of the above Foo and Bar classes,
if I open a Transcript and run in a Workspace :

|p| 
p _ Bar new.
Bar addFooBar.
p foobar.

will print in an open Transcript

in Foo run:with:in:

Again, I think this could/or should be documented on wiki.squeak.org,
but what happens is, I think, that if  I dynamically add a message (method)
implementation to class Bar, using addFooBar, which is installing
a method #foobar using addSelector:withMethod:, then the VM dispatched
a run:with:in message to the 'method' object, which need not be a actually,
a subclass of CompiledMethod.

Also some other selectors flushCache, selector: and methodClass: seem 
necessary for this feature to work.

By subclassing AbstractObjectsAsMethod, on the other hand, it is not required
to implement flushCache, selector: and methodClass: as AbstractObjectsAsMethod
is doing that, so perhaps the intented usage is to subclass

 AbstractObjectsAsMethod

That is why in the above example I do:

 AbstractObjectsAsMethod subclass: #Foo

If this is a standard Squeak feature, it could be on the wiki.squeak.org;
I was not able to find info on it.

David Stes
 
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