Present only on data change.

Parent presenters shows `Object new` by default,
so they "always change".

src/MiniMVP.js

@@ -4,7 +4,84 @@ var $pkg = $core.addPackage("MiniMVP");
 $pkg.innerEval = function (expr) { return eval(expr); };
 $pkg.transport = {"type":"amd","amdNamespace":"mini-mvp"};
 
-$core.addClass("MiniPresenter", $globals.Object, ["frame", "dataBlock"], "MiniMVP");
+$core.addClass("MiniPresenter", $globals.Object, ["frame", "dataBlock", "currentData"], "MiniMVP");
+$core.addMethod(
+$core.method({
+selector: "currentData",
+protocol: "accessing",
+//>>excludeStart("ide", pragmas.excludeIdeData);
+args: [],
+source: "currentData\x0a\x09^ currentData",
+referencedClasses: [],
+//>>excludeEnd("ide");
+pragmas: [],
+messageSends: []
+}, function ($methodClass){ return function (){
+var self=this,$self=this;
+return $self.currentData;
+
+}; }),
+$globals.MiniPresenter);
+
+$core.addMethod(
+$core.method({
+selector: "currentData:",
+protocol: "accessing",
+//>>excludeStart("ide", pragmas.excludeIdeData);
+args: ["anObject"],
+source: "currentData: anObject\x0a\x09currentData := anObject",
+referencedClasses: [],
+//>>excludeEnd("ide");
+pragmas: [],
+messageSends: []
+}, function ($methodClass){ return function (anObject){
+var self=this,$self=this;
+$self.currentData=anObject;
+return self;
+
+}; }),
+$globals.MiniPresenter);
+
+$core.addMethod(
+$core.method({
+selector: "currentData:ifChangedToNil:ifChangedToNotNil:",
+protocol: "actions",
+//>>excludeStart("ide", pragmas.excludeIdeData);
+args: ["anObject", "aBlock", "anotherBlock"],
+source: "currentData: anObject ifChangedToNil: aBlock ifChangedToNotNil: anotherBlock\x0a\x09| oldData newData |\x0a\x09oldData := self currentData.\x0a\x09self currentData: anObject.\x0a\x09newData := self currentData.\x0a\x09oldData = newData ifFalse: [\x0a\x09\x09newData ifNil: [ aBlock value ] ifNotNil: [ anotherBlock value: newData ] ]",
+referencedClasses: [],
+//>>excludeEnd("ide");
+pragmas: [],
+messageSends: ["currentData", "currentData:", "ifFalse:", "=", "ifNil:ifNotNil:", "value", "value:"]
+}, function ($methodClass){ return function (anObject,aBlock,anotherBlock){
+var self=this,$self=this;
+var oldData,newData;
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+return $core.withContext(function($ctx1) {
+//>>excludeEnd("ctx");
+var $1;
+oldData=[$self._currentData()
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+,$ctx1.sendIdx["currentData"]=1
+//>>excludeEnd("ctx");
+][0];
+$self._currentData_(anObject);
+newData=$self._currentData();
+if(!$core.assert($recv(oldData).__eq(newData))){
+$1=newData;
+if($1 == null || $1.a$nil){
+$recv(aBlock)._value();
+} else {
+$recv(anotherBlock)._value_(newData);
+}
+}
+return self;
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+}, function($ctx1) {$ctx1.fill(self,"currentData:ifChangedToNil:ifChangedToNotNil:",{anObject:anObject,aBlock:aBlock,anotherBlock:anotherBlock,oldData:oldData,newData:newData})});
+//>>excludeEnd("ctx");
+}; }),
+$globals.MiniPresenter);
+
 $core.addMethod(
 $core.method({
 selector: "dataBlock",
@@ -133,26 +210,34 @@ selector: "refresh",
 protocol: "actions",
 //>>excludeStart("ide", pragmas.excludeIdeData);
 args: [],
-source: "refresh\x0a\x09self dataBlock value\x0a\x09\x09ifNil: [ self hide ]\x0a\x09\x09ifNotNil: [ :data | self show; present: data ]",
+source: "refresh\x0a\x09self\x0a\x09\x09currentData: self dataBlock value\x0a\x09\x09ifChangedToNil: [ self hide ]\x0a\x09\x09ifChangedToNotNil: [ :data | self show; present: data ]",
 referencedClasses: [],
 //>>excludeEnd("ide");
 pragmas: [],
-messageSends: ["ifNil:ifNotNil:", "value", "dataBlock", "hide", "show", "present:"]
+messageSends: ["currentData:ifChangedToNil:ifChangedToNotNil:", "value", "dataBlock", "hide", "show", "present:"]
 }, function ($methodClass){ return function (){
 var self=this,$self=this;
 //>>excludeStart("ctx", pragmas.excludeDebugContexts);
 return $core.withContext(function($ctx1) {
 //>>excludeEnd("ctx");
-var $1;
-$1=$recv($self._dataBlock())._value();
-if($1 == null || $1.a$nil){
-$self._hide();
-} else {
-var data;
-data=$1;
+$self._currentData_ifChangedToNil_ifChangedToNotNil_($recv($self._dataBlock())._value(),(function(){
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+return $core.withContext(function($ctx2) {
+//>>excludeEnd("ctx");
+return $self._hide();
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+}, function($ctx2) {$ctx2.fillBlock({},$ctx1,1)});
+//>>excludeEnd("ctx");
+}),(function(data){
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+return $core.withContext(function($ctx2) {
+//>>excludeEnd("ctx");
 $self._show();
-$self._present_(data);
-}
+return $self._present_(data);
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+}, function($ctx2) {$ctx2.fillBlock({data:data},$ctx1,2)});
+//>>excludeEnd("ctx");
+}));
 return self;
 //>>excludeStart("ctx", pragmas.excludeDebugContexts);
 }, function($ctx1) {$ctx1.fill(self,"refresh",{})});
@@ -473,11 +558,11 @@ selector: "in:",
 protocol: "instance creation",
 //>>excludeStart("ide", pragmas.excludeIdeData);
 args: ["aDommable"],
-source: "in: aDommable\x0a\x09^ super shows: [ true ] in: aDommable",
-referencedClasses: [],
+source: "in: aDommable\x0a\x09^ super shows: [ Object new ] in: aDommable",
+referencedClasses: ["Object"],
 //>>excludeEnd("ide");
 pragmas: [],
-messageSends: ["shows:in:"]
+messageSends: ["shows:in:", "new"]
 }, function ($methodClass){ return function (aDommable){
 var self=this,$self=this;
 //>>excludeStart("ctx", pragmas.excludeDebugContexts);
@@ -488,8 +573,13 @@ return [(
 $ctx1.supercall = true,
 //>>excludeEnd("ctx");
 ($methodClass.superclass||$boot.nilAsClass).fn.prototype._shows_in_.call($self,(function(){
-return true;
-
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+return $core.withContext(function($ctx2) {
+//>>excludeEnd("ctx");
+return $recv($globals.Object)._new();
+//>>excludeStart("ctx", pragmas.excludeDebugContexts);
+}, function($ctx2) {$ctx2.fillBlock({},$ctx1,1)});
+//>>excludeEnd("ctx");
 }),aDommable))
 //>>excludeStart("ctx", pragmas.excludeDebugContexts);
 ,$ctx1.supercall = false

src/MiniMVP.st

@@ -1,10 +1,18 @@
 Smalltalk createPackage: 'MiniMVP'!
 Object subclass: #MiniPresenter
-	slots: {#frame. #dataBlock}
+	slots: {#frame. #dataBlock. #currentData}
 	package: 'MiniMVP'!
 
 !MiniPresenter methodsFor: 'accessing'!
 
+currentData
+	^ currentData
+!
+
+currentData: anObject
+	currentData := anObject
+!
+
 dataBlock
 	^ dataBlock
 !
@@ -23,14 +31,24 @@ frame: anObject
 
 !MiniPresenter methodsFor: 'actions'!
 
+currentData: anObject ifChangedToNil: aBlock ifChangedToNotNil: anotherBlock
+	| oldData newData |
+	oldData := self currentData.
+	self currentData: anObject.
+	newData := self currentData.
+	oldData = newData ifFalse: [
+		newData ifNil: [ aBlock value ] ifNotNil: [ anotherBlock value: newData ] ]
+!
+
 present: anObject
 	self subclassResponsibility
 !
 
 refresh
-	self dataBlock value
-		ifNil: [ self hide ]
-		ifNotNil: [ :data | self show; present: data ]
+	self
+		currentData: self dataBlock value
+		ifChangedToNil: [ self hide ]
+		ifChangedToNotNil: [ :data | self show; present: data ]
 ! !
 
 !MiniPresenter methodsFor: 'private'!
@@ -125,6 +143,6 @@ present: anObject
 !MiniParentPresenter class methodsFor: 'instance creation'!
 
 in: aDommable
-	^ super shows: [ true ] in: aDommable
+	^ super shows: [ Object new ] in: aDommable
 ! !