--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/IndirectValue.st	Thu Aug 28 12:38:04 2003 +0200
@@ -0,0 +1,109 @@
+"{ Package: 'stx:libview2' }"
+
+ValueModel subclass:#IndirectValue
+	instanceVariableNames:'valueHolder'
+	classVariableNames:''
+	poolDictionaries:''
+	category:'Interface-Support-Models'
+!
+
+!IndirectValue class methodsFor:'documentation'!
+
+documentation
+"
+    IndirectValue referes to another valueHolder and presents that holders value
+    as my own value.
+    However, the holder can be changed, which results in a change message from myself.
+    Can be used if a valueHolder is needed which represents different values over
+    time, for example, a line/column holder for a notebook-like multi-codeView 
+    application, where the line/col holder is switched whenever the tab is switched.
+    (use an IndirectValue as holder of the line/col labels).
+
+    [author:]
+        Claus Gittinger
+"
+!
+
+examples
+"
+    a label alternatively showing the value of 2 other valueHolders:
+                                                                        [exBegin]
+        |holder1 holder2 indirVal lbl|
+
+        holder1 := '1' asValue.
+        holder2 := '2' asValue.
+        indirVal := IndirectValue for:holder1.
+
+        lbl := Label new.
+        lbl labelChannel:indirVal.
+        lbl open.
+        lbl waitUntilVisible.
+        
+        Delay waitForSeconds:2.
+        indirVal valueHolder:holder2.
+
+        Delay waitForSeconds:2.
+        indirVal valueHolder:holder1.
+                                                                        [exEnd]
+"
+! !
+
+!IndirectValue class methodsFor:'instance creation'!
+
+for:aValueHolder
+    "return a new IndirectValue presenting aValueHolder"
+
+    ^ self new setValueHolder:aValueHolder
+! !
+
+!IndirectValue methodsFor:'accessing'!
+
+setValue:newValue 
+    "physically set my value, without change notifications"
+
+    valueHolder setValue:newValue
+!
+
+setValueHolder:aValueHolder
+    "change my holder"
+
+    valueHolder notNil ifTrue:[
+        valueHolder removeDependent:self.
+    ].
+    valueHolder := aValueHolder.
+    valueHolder notNil ifTrue:[
+        valueHolder addDependent:self.
+    ].
+!
+
+value 
+    "return my value"
+
+    ^ valueHolder value
+!
+
+valueHolder:aValueHolder
+    "change my holder"
+
+    |oldValue|
+
+    oldValue := valueHolder value.
+    self setValueHolder:aValueHolder.
+    oldValue ~~ valueHolder value ifTrue:[
+        self changed:#value
+    ].
+! !
+
+!IndirectValue methodsFor:'change and update'!
+
+update:something with:aParameter from:someone
+    "the holder I depend on has changed - send a change notification to my dependents"
+
+    self changed:#value
+! !
+
+!IndirectValue class methodsFor:'documentation'!
+
+version
+    ^ '$Header: /cvs/stx/stx/libview2/IndirectValue.st,v 1.1 2003-08-28 10:38:04 cg Exp $'
+! !