My question is this: Instead of providing Object#objectSpecificMethod
a string, would it be possible to provide it a block?
Yes, but it is not in the basic class library. You can define a
subclass of CompiledMethod that will forward the message to a block.
Something like this (I'm using 2.95x syntax; if you have an older
version as I think, it will be easy to convert it to the old syntax; or
it will whet your appetite so you'll download the latest version and
compile it).
CompiledMethod subclass: MethodBlock [
| closure |
MethodBlock class >> on: aBlock [
^(self numArgs: aBlock numArgs) closure: aBlock
]
closure: aBlock [
closure := aBlock
]
valueWithReceiver: anObject withArguments: args [
^closure valueWithArguments: args
]
]
Behavior subclass: ObjectSpecificBehavior [
Behavior >> isObjectSpecific [ ^false ]
isObjectSpecific [ ^true ]
]
Object extend [
implantObjectSpecificBehavior [
| subclass |
self class isObjectSpecific ifFalse: [
subclass := ObjectSpecificBehavior new.
subclass superclass: self class.
self changeClassTo: subclass ]
]
objectSpecificMethod: aString [
self implantObjectSpecificBehavior.
self class compile: aString
]
objectSpecificMethod: selector do: aBlock [
self implantObjectSpecificBehavior.
self class
addSelector: selector
withMethod: (MethodBlock on: aBlock )
]
]
| obj |
obj := 1 to: 20.
obj
objectSpecificMethod: #every:
do: [ :n | obj atAll: (n to: obj size by: 3) ].
(obj every: 3) printNl "(3 6 9 12 15 18 )"
As you can see from the example, blocks don't have access to "self" and
instance variables available. This is by design. In Ruby, @abc syntax
is resolved at run-time, while in Smalltalk it is resolved at
compile-time (you need to know the list of instance variables at
compile-time). On the other hand, 99% of the time you can access self
from the enclosing environment ("obj" in the example), and you gain the
possibility to access the enclosing environment's "self" and instance
variables.
Paolo
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