Add callback invocation capabilities.

src/ActiveExpressions-Core.package/ActiveExpression.class/class/monitoring..st

@@ -1,4 +1,6 @@
 instance creation
 monitoring: aBlock
 
-	^ self new setMonitoredBlock: aBlock
+	^ self basicNew 
+			setMonitoredBlock: aBlock;
+			initialize

src/ActiveExpressions-Core.package/ActiveExpression.class/instance/currentValue.st

@@ -0,0 +1,4 @@
+accessing
+currentValue
+
+	 ^ monitoredBlock value

src/ActiveExpressions-Core.package/ActiveExpression.class/instance/initialize.st

@@ -0,0 +1,5 @@
+initialize-release
+initialize
+
+	super initialize.
+	self setLastValue: self currentValue

src/ActiveExpressions-Core.package/ActiveExpression.class/instance/invokeCallback..st

@@ -0,0 +1,4 @@
+callbacks
+invokeCallback: aBlock
+
+	aBlock value

src/ActiveExpressions-Core.package/ActiveExpression.class/instance/invokeCallback.lastValue.newValue..st

@@ -0,0 +1,7 @@
+callbacks
+invokeCallback: aBlock lastValue: old newValue: new
+
+	aBlock argumentCount = 0 ifTrue: [^ aBlock value].
+	aBlock argumentCount = 1 ifTrue: [^ aBlock valueWithArguments: { new }].
+	aBlock argumentCount = 2 ifTrue: [^ aBlock valueWithArguments: { old . new }].
+	self error: 'Callback requires too many arguments'

src/ActiveExpressions-Core.package/ActiveExpression.class/instance/lastValue.st

@@ -0,0 +1,4 @@
+accessing
+lastValue
+
+	^ lastValue

src/ActiveExpressions-Core.package/ActiveExpression.class/instance/setLastValue..st

@@ -0,0 +1,4 @@
+private
+setLastValue: anObject
+
+	lastValue := anObject

src/ActiveExpressions-Core.package/ActiveExpression.class/instance/update.st

@@ -0,0 +1,9 @@
+change
+update
+
+	| newValue oldValue |
+	oldValue := self lastValue.
+	newValue := self currentValue.
+	oldValue ~~ newValue ifTrue: [
+		self setLastValue: newValue.
+		self callbacks do: [:each | self invokeCallback: each lastValue: oldValue newValue: newValue]]

src/ActiveExpressions-Core.package/ActiveExpression.class/methodProperties.json

@@ -1,10 +1,17 @@
 {
 	"class" : {
-		"monitoring:" : "sl 12/26/2017 09:55" },
+		"monitoring:" : "sl 12/26/2017 18:55" },
 	"instance" : {
 		"callbacks" : "sl 12/26/2017 10:15",
+		"currentValue" : "sl 12/26/2017 10:49",
+		"initialize" : "sl 12/26/2017 10:48",
+		"invokeCallback:" : "sl 12/26/2017 10:36",
+		"invokeCallback:lastValue:newValue:" : "sl 12/26/2017 10:46",
+		"lastValue" : "sl 12/26/2017 18:49",
 		"monitoredBlock" : "sl 12/23/2017 10:14",
 		"onChangeDo:" : "sl 12/26/2017 10:11",
 		"printOn:" : "sl 12/26/2017 10:04",
 		"registerCallback:" : "sl 12/26/2017 10:13",
-		"setMonitoredBlock:" : "sl 12/26/2017 09:53" } }
+		"setLastValue:" : "sl 12/26/2017 18:43",
+		"setMonitoredBlock:" : "sl 12/26/2017 09:53",
+		"update" : "sl 12/26/2017 18:49" } }

src/ActiveExpressions-Core.package/ActiveExpression.class/properties.json

@@ -7,7 +7,8 @@
 	"commentStamp" : "",
 	"instvars" : [
 		"monitoredBlock",
-		"callbacks" ],
+		"callbacks",
+		"lastValue" ],
 	"name" : "ActiveExpression",
 	"pools" : [
 		 ],

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/instance/setUp.st

@@ -0,0 +1,7 @@
+running
+setUp
+
+	value := 42.
+	callbackCount := 0.
+	activeExpression := ActiveExpression monitoring: [value].
+	activeExpression onChangeDo: [callbackCount := callbackCount + 1]

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/instance/testCallbackInvocationWhenValueIdentityHasChanged.st

@@ -0,0 +1,6 @@
+tests - callbacks
+testCallbackInvocationWhenValueIdentityHasChanged
+
+	value := 2.
+	activeExpression update.
+	self assert: 1 equals: callbackCount

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/instance/testCallbackInvocationWith1Argument.st

@@ -0,0 +1,7 @@
+tests - callbacks
+testCallbackInvocationWith1Argument
+
+	activeExpression onChangeDo: [:new |
+		self assert: 1 equals: new].
+	value := 1.
+	activeExpression update

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/instance/testCallbackInvocationWith2Arguments.st

@@ -0,0 +1,8 @@
+tests - callbacks
+testCallbackInvocationWith2Arguments
+
+	activeExpression onChangeDo: [:old :new | 
+		self assert: 42 equals: old.
+		self assert: 1 equals: new].
+	value := 1.
+	activeExpression update

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/instance/testCallbackInvocationWithMoreThan3ArgumentsFails.st

@@ -0,0 +1,6 @@
+tests - callbacks
+testCallbackInvocationWithMoreThan3ArgumentsFails
+
+	activeExpression onChangeDo: [:one :two :three | 42].
+	value := 1.
+	self should: [activeExpression update] raise: Error

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/instance/testInitializesToCurrentValue.st

@@ -0,0 +1,4 @@
+tests
+testInitializesToCurrentValue
+
+	self assert: 42 equals: activeExpression lastValue

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/instance/testNoCallbackInvocationWhenValueIdentityHasNotChanged.st

@@ -0,0 +1,5 @@
+tests - callbacks
+testNoCallbackInvocationWhenValueIdentityHasNotChanged
+
+	activeExpression update.
+	self assert: 0 equals: callbackCount

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/instance/testRemembersOldValue.st

@@ -0,0 +1,6 @@
+tests
+testRemembersOldValue
+
+	value := 1.
+	activeExpression update.
+	self assert: 1 equals: activeExpression lastValue

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/methodProperties.json

@@ -2,4 +2,11 @@
 	"class" : {
 		 },
 	"instance" : {
-		"testTruth" : "sl 12/23/2017 10:18" } }
+		"setUp" : "sl 12/26/2017 18:51",
+		"testCallbackInvocationWhenValueIdentityHasChanged" : "sl 12/26/2017 10:35",
+		"testCallbackInvocationWith1Argument" : "sl 12/26/2017 19:05",
+		"testCallbackInvocationWith2Arguments" : "sl 12/26/2017 19:05",
+		"testCallbackInvocationWithMoreThan3ArgumentsFails" : "sl 12/26/2017 19:01",
+		"testInitializesToCurrentValue" : "sl 12/26/2017 18:51",
+		"testNoCallbackInvocationWhenValueIdentityHasNotChanged" : "sl 12/26/2017 18:57",
+		"testRemembersOldValue" : "sl 12/26/2017 19:09" } }

src/ActiveExpressions-Tests.package/ActiveExpressionTests.class/properties.json

@@ -6,7 +6,9 @@
 		 ],
 	"commentStamp" : "",
 	"instvars" : [
-		 ],
+		"value",
+		"activeExpression",
+		"callbackCount" ],
 	"name" : "ActiveExpressionTests",
 	"pools" : [
 		 ],