--- a/extensions.st	Fri Oct 06 14:37:32 2006 +0200
+++ b/extensions.st	Mon Oct 09 12:46:05 2006 +0200
@@ -1,19 +1,386 @@
 "{ Package: 'stx:libbasic2' }"
 !
 
-!Object methodsFor:'converting'!
+!Object methodsFor:'dependents-interests'!
+
+addInterest:anInterest
+    "install an interest forwarder.
+     Here, we use the nonWeakDependencies."
+
+    self addNonWeakDependent:anInterest
+
+    "Created: 14.10.1996 / 22:27:34 / stefan"
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+expressInterestIn:aspect for:anObject sendBack:aSelector
+    "arrange for aSelector to be sent to anObject whenever the receiver
+     changes aspect."
+
+    "/ for now, use an interestConverter, which is somewhat less efficient.
+    "/ In the future, a more intelligent DependencyCollection class is planned for
+
+    self addInterest:(InterestConverter 
+                            destination:anObject 
+                            selector:aSelector 
+                            aspect:aspect)
+
+    "
+     |p b|
+
+     b := [Transcript showCR:' -> the point changed'].
+
+     p := Point new.
+     Transcript showCR:'interest in #foo:'.
+     p expressInterestIn:#foo for:b sendBack:#value.
+     p x:1.
+     Transcript showCR:'now changing #bar ... (expect no notification)'.
+     p changed:#bar.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'now changing #foo ... (expect notification)'.
+     p changed:#foo.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'no more interest in #foo:'.
+     p retractInterestIn:#foo for:b.
+     Transcript showCR:'now changing #foo ... (expect no notification)'.
+     p changed:#foo.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'interest in #bar now:'.
+     p expressInterestIn:#bar for:b sendBack:#value.
+     Transcript showCR:'now changing #foo ... (expect no notification)'.
+     p changed:#foo.
+     Transcript showCR:'now changing #bar ... (expect notification)'.
+     p changed:#bar.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'interest in #foo now:'.
+     p expressInterestIn:#foo for:b sendBack:#value.
+     Transcript showCR:'now changing #foo ... (expect notification)'.
+     p changed:#foo.
+     Transcript showCR:'now changing #bar ... (expect notification)'.
+     p changed:#bar.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'no more interests:'.
+     p retractInterestsFor:b.
+     Transcript showCR:'now changing #foo ... (expect no notification)'.
+     p changed:#foo.
+     Transcript showCR:'now changing #bar...  (expect no notification)'.
+     p changed:#bar.
+     Transcript cr.
+
+     p release.
+    "
 
-!! anObject
-    "return a cons with the receiver as car and the argument as cdr"
+    "Created: 19.4.1996 / 10:26:22 / cg"
+    "Modified: 19.4.1996 / 12:34:08 / cg"
+    "Modified: 14.10.1996 / 22:28:20 / stefan"
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+interests
+    "return a Collection of interests - empty if there is none.
+     Here, we use the nonWeakDependents for interests."
+
+    ^ self nonWeakDependents
+
+    "Created: / 14.10.1996 / 22:20:51 / stefan"
+    "Modified: / 30.1.1998 / 14:07:35 / cg"
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+interestsFor:someOne
+    "return a collection of interests of someOne - empty if there is none."
+
+    |coll deps|
+
+    deps := self interests.
+    deps size == 0 ifTrue:[^ #()].
+
+    coll := IdentitySet new.
+
+    deps do:[:dep |
+        (dep isInterestConverter) ifTrue:[
+            dep destination == someOne ifTrue:[
+                coll add:dep.
+            ]
+        ]
+    ].
+    ^ coll
+
+    "Created: / 30.1.1998 / 14:02:26 / cg"
+    "Modified: / 30.1.1998 / 14:08:24 / cg"
+! !
 
-    ^ Cons car:self cdr:anObject
+!Object methodsFor:'dependents-interests'!
+
+onChangeEvaluate:aBlock
+    "arrange for aBlock to be evaluated whenever the receiver changes."
+
+    ^ self onChangeSend:#value to:aBlock
+
+    "
+     |p b|
+
+     b := [Transcript showCR:' -> the point changed'].
+
+     p := Point new.
+     Transcript showCR:'interest in #foo:'.
+     p onChangeEvaluate:b.
+     p x:1.
+     Transcript showCR:'now changing #bar ... (expect no notification)'.
+     p changed:#bar.
+
+     p retractInterests.
+     p changed:#bar.
+    "
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+onChangeSend:aSelector to:anObject
+    "arrange for aSelector to be sent to anObject whenever the receiver
+     changes."
+
+    "/ for now, use an interestConverter, which is somewhat less efficient.
+    "/ In the future, a more intelligent DependencyCollection class is planned for
+
+    ((self interests ? #())
+        contains:[:anInterest |
+            (anInterest isInterestConverter)
+            and:[ anInterest destination == anObject
+            and:[ anInterest selector == aSelector]]
+        ])
+            ifTrue:[^ self].
+
+    self addInterest:(InterestConverter 
+                          destination:anObject 
+                          selector:aSelector)
 
     "
-     (1 !! 2)                
-     (#car !! #cdr)          
-     (1 !! (2 !! (3 !! nil)))    
-     (1 !! 2) !! (2 !! 3)    
+     |p b|
+
+     b := [Transcript showCR:'the point changed'].
+
+     p := Point new.
+     p onChangeSend:#value to:b.
+     p x:1.
+     Transcript showCR:'now changing'.
+     p changed.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'now changing'.
+     p changed.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'no more interest'.
+     p retractInterestsFor:b.
+     Transcript showCR:'now changing again'.
+     p changed.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'interest again'.
+     p onChangeSend:#value to:b.
+     Transcript showCR:'now changing again'.
+     p changed.
+     Transcript cr.
+    "
+
+    "Created: 19.4.1996 / 10:26:38 / cg"
+    "Modified: 19.4.1996 / 12:34:26 / cg"
+    "Modified: 14.10.1996 / 22:28:27 / stefan"
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+removeInterest:anInterest
+    "remove an interest forwarder.
+     Here, we use the nonWeakDependencies."
+
+    self removeNonWeakDependent:anInterest
+
+    "Created: 14.10.1996 / 22:21:59 / stefan"
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+retractInterestIn:aspect for:someOne
+    "remove the interest of someOne in the receiver changing aspect
+     (as installed with #expressInterestIn:for:sendBack:)."
+
+    "/ for now, remove the interestConverter.
+    "/ In the future, a more intelligent DependencyCollection class is planned for
+
+    self retractInterestsForWhich:[:i | (i aspect == aspect) and:[i destination == someOne]]
+
     "
+     |p b|
+
+     b := [Transcript showCR:'the point changed'].
+
+     p := Point new.
+     Transcript showCR:'interest in #foo'.
+     p expressInterestIn:#foo for:b sendBack:#value.
+     p x:1.
+     Transcript showCR:'now changing #bar'.
+     p changed:#bar.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'now changing #foo'.
+     p changed:#foo.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'no more interest in #foo'.
+     p retractInterestIn:#foo for:b.
+     Transcript showCR:'now changing #foo'.
+     p changed:#foo.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'interest in #bar now'.
+     p expressInterestIn:#bar for:b sendBack:#value.
+     Transcript showCR:'now changing #foo'.
+     p changed:#foo.
+     Transcript showCR:'now changing #bar'.
+     p changed:#bar.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'interest in #foo now'.
+     p expressInterestIn:#foo for:b sendBack:#value.
+     Transcript showCR:'now changing #foo'.
+     p changed:#foo.
+     Transcript showCR:'now changing #bar'.
+     p changed:#bar.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'no more interests'.
+     p retractInterestsFor:b.
+     Transcript showCR:'now changing #foo'.
+     p changed:#foo.
+     Transcript showCR:'now changing #bar'.
+     p changed:#bar.
+     Transcript cr.
+    "
+
+    "Created: / 19.4.1996 / 10:27:11 / cg"
+    "Modified: / 14.10.1996 / 22:21:19 / stefan"
+    "Modified: / 30.1.1998 / 14:05:34 / cg"
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+retractInterests
+    "remove all interests in the receiver changing aspect
+     (as installed with #expressInterestIn:for:sendBack:)."
+
+    "/ for now, remove the interestConverter.
+    "/ In the future, a more intelligent DependencyCollection class is planned for
+
+    self retractInterestsForWhich:[:i | true ]
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+retractInterestsFor:someOne
+    "remove the interest of someOne in the receiver 
+     (as installed with #onChangeSend:to:)."
+
+    "/ for now, remove the interestConverter.
+    "/ In the future, a more intelligent DependencyCollection class is planned for
+
+    self retractInterestsForWhich:[:i | i destination == someOne ]
+
+    "
+     |p b|
+
+     b := [Transcript showCR:'the point changed'].
+
+     p := Point new.
+     p onChangeSend:#value to:b.
+     p x:1.
+     Transcript showCR:'now changing'.
+     p changed.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'now changing'.
+     p changed.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'no more interest'.
+     p retractInterestsFor:b.
+     Transcript showCR:'now changing again'.
+     p changed.
+     Transcript cr.
+
+     Delay waitForSeconds:1.
+     Transcript showCR:'interest again'.
+     p onChangeSend:#value to:b.
+     Transcript showCR:'now changing again'.
+     p changed.
+     Transcript cr.
+    "
+
+    "Created: / 19.4.1996 / 10:23:46 / cg"
+    "Modified: / 14.10.1996 / 22:21:25 / stefan"
+    "Modified: / 30.1.1998 / 14:04:52 / cg"
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+retractInterestsForWhich:aBlock
+    "remove all interests in the receiver changing aspect
+     (as installed with #expressInterestIn:for:sendBack:)."
+
+    "/ for now, remove the interestConverter.
+    "/ In the future, a more intelligent DependencyCollection class is planned for
+
+    |deps coll|
+
+    deps := self interests.
+    deps size ~~ 0 ifTrue:[
+        "/ cannot removeDependent within the loop - the interests collection rehashes
+        coll := OrderedCollection new.
+        deps do:[:dep |
+            dep isInterestConverter ifTrue:[
+                (aBlock value:dep) ifTrue:[coll add:dep].
+            ]
+        ].
+        coll do:[:dep |
+            self removeInterest:dep.
+        ].
+    ].
+! !
+
+!Object methodsFor:'dependents-interests'!
+
+retractInterestsIn:aspect
+    "remove all interests in the receiver changing aspect
+     (as installed with #expressInterestIn:for:sendBack:)."
+
+    "/ for now, remove the interestConverter.
+    "/ In the future, a more intelligent DependencyCollection class is planned for
+
+    self retractInterestsForWhich:[:i | i aspect == aspect ]
 ! !
 
 !Object methodsFor:'dependents-st/v event simulation'!