0
Diving Deep with the Flex
  Component Lifecycle
        Joshua Jamison
          EffectiveUI
      www.effectiveui.com
     ...
Who am I?



   ‣ Joshua Jamison
    •   Software Architect @ EffectiveUI
Who are you (hopefully)?


     ‣ Beginner to intermediate level developers
     ‣ Anyone who doesn’t currently understand...
What’s this about, anyway?




     ‣ Flex component lifecycle
     ‣ Flex frame cycle (“elastic racetrack”)
Flex Component Lifecycle

     ‣ What is it?
       • The way the framework interacts with
         every Flex component
 ...
Elastic Racetrack: introduction




                                       image courtesy of Ted Patrick




 ‣ Flex compo...
A frame in AS3




                 image courtesy of Sean Christmann
Phases of the Lifecycle

      ‣ 3 Main Phases:
      ‣ BIRTH:
        •  construction, con guration,
           attachmen...
Birth
Congratulations: You’re about to have a component.
Construction


Birth
   construction
   con guration
   attachment
   initialization
Life
Death
What is a constructor?




                    ‣ A function called to instantiate (create in
                     memory) ...
How is a constructor invoked?



                                Actionscript:
                    var theLabel : Label = ...
What does a constructor have access to?




                    ‣ Properties on the class
                    ‣ Methods on...
What does an ActionScript3
  constructor look like?
            public function ComponentName()
            {
            ...
What does an MXML constructor
  look like?
          ‣ No need to de           ne one. In fact, if you try
               ...
What should a constructor do?

                    ‣ Not much.
                              Since the component’s
       ...
Don’t create or attach children in
   the constructor



                    ‣ It’s best to delay the cost of createChildr...
Con guration


Birth
   construction
   con guration
   attachment
   initialization
Life
Death
Con guration
                    ‣ The process of assigning values to
                      properties on objects
        ...
Hooray: Sample code!


                    <mx:Application ...>
                    	 ...
                      <local:Sam...
Con guration and Containers

                    ‣ Containers must not expect their children
                     have to ...
Con guration Optimization



                    ‣ To avoid performance bottlenecks, make
                      your sette...
Attachment


Birth
   construction
   con guration
   attachment
   initialization
Life
Death
What is attachment?



                    ‣ Adding a component to the display list
                     (addChild, addChi...
Consider this component:
	   public class A extends UIComponent
	
	
    {
    	    public function A() {
                 ...
And this application:
<mx:Application ...>
	 <mx:Script>
	 	 <![CDATA[
	 	 	 override protected function createChildren() ...
But what about this application?
<mx:Application ...>
	   <mx:Script>
	   	    <![CDATA[
	   	    	   override protected f...
Initialization


Birth
   construction
   con guration
   attachment
   initialization
Life
Death
Initialization

                      ‣ 2 phases, 3 events:

                               1.   ‘preInitialize’ dispatche...
createChildren()
     ‣   MXML uses the createChildren() method to add
         children to containers
     ‣   Override t...
rst validation pass

                    ‣ Invalidation is not part of initialization -
                      only Validat...
Life
They grow up so fast.
Invalidation



Birth
Life
   invalidation
   validation
   interaction
Death
Invalidation / Validation cycle
     ‣ Flex imposes deferred validation on the
       Flash API
        • goal: defer scre...
Invalidation / Validation theory




      ‣ First, a little theory.
Deferment

    ‣ Deferment is the central concept to
     understand in the component Life-cycle

    ‣ Use private variab...
Text-book example
Bad:
public function set text(value:String):void
{
    myLabel.text = value;
// Possible Error! during f...
The Elastic Racetrack revisited




                         image courtesy of Sean Christmann


  Invalidation occurs here
Invalidation methods

                  ‣ invalidateProperties()
                    •  Any property changes
             ...
Invalidation example 1
<mx:Application>
	 <mx:Script>
	 	 <![CDATA[
	 	 	 import mx.collections.ArrayCollection;
	 	 	
	 	...
Invalidation example 2
    public class BadList extends VBox
	    {
	    	 private var _dataProvider : ArrayCollection;
	 ...
Invalidation example 3
    public class GoodList extends VBox
	    {
	    	   private var _dataProvider : ArrayCollection;...
Validation



Birth
Life
   invalidation
   validation
   interaction
Death
The Elastic Racetrack revisited




              Validation occurs here
Validation

                  ‣ Apply the changes deferred during
                    invalidation
                  ‣ Upd...
commitProperties()


                  ‣ Ely says: “Calculate and commit the effects
                    of changes to prop...
commitProperties() cont.

                  ‣ ALL changes based on property and data
                    events go here
  ...
measure()

                  ‣ Component calculates its preferred
                    (“default”) and minimum proportions
...
overriding measure()

                  ‣ Used for dynamic layout containers (VBox,
                    etc.)
            ...
measure() cont.




                  ‣ Not reliable - Framework optimizes away
                   any calls to measure it...
updateDisplayList()

                  ‣ All drawing and layout code goes here,
                    making this the core m...
Overriding updateDisplayList()

                  ‣ Usually call super.updateDisplayList()        rst
                    ...
Elastic Racetrack cont.

      ‣ User Actions
       • Dispatch invalidation events
       • Interact with any non-validat...
Elastic Racetrack Cont.

     ‣ Invalidate Action
       • Process all validation calls
     ‣ Render Action
       • Do t...
The Elastic Racetrack revisited




     Queued Invalidation
              Deferred Validation
                           ...
Interaction



Birth
Life
   invalidation
   validation
   interaction
Death
How do objects know when
   something happens?
                  ‣ Events: objects passed around when
                    ...
Bene ts of Loosely-Coupled
   Architectures


                  ‣ Everything becomes more reusable
                  ‣ Com...
Who can dispatch events?


                  ‣ Subclasses of EventDispatcher
                   •  EventDispatcher inherit...
How to tell events apart?



                  ‣ Event class
                    • Different classes allow for customized
 ...
Common Events


                  ‣ Event.CHANGE
                  ‣ MouseEvent.CLICK
                  ‣ FlexEvent.CREATI...
Handling Events



                  ‣ <mx:Button id=”theButton”
                    click=”callThisFunction(event)”/>
   ...
Event Propagation
       ‣   Three phases: Capturing, Targeting, Bubbling



             Application                  App...
Event Propagation
          ‣   Three phases: Capturing, Targeting, Bubbling
          <mx:Application 	initialize="onInit...
Event Propagation
                  ----------------------------------------------------------
                  TARGET: b...
Stopping events from propagating

                  ‣ stopPropagation() : Prevents processing
                    of any e...
target vs. currentTarget


                  ‣ target: the object that dispatched the
                    event (doesn’t c...
Dispatching events from custom
   components
        ‣ MXML:
           <mx:Metadata>
               [Event(name="atePizza...
Death
All good things come to an end.
Detachment



Birth
Life
Death
   detachment
   garbage
   collection
Detachment

                ‣ “Detachment” refers to the process of
                  removing a child from the display li...
Detachment cont.

                ‣ Re-parenting isn’t cheap, but it’s cheaper
                  than re-creating the same...
Garbage Collection



Birth
Life
Death
   detachment
   garbage
   collection
Garbage Collection

                ‣ The process by which memory is returned
                  to the system
            ...
Conclusion



     ‣ Defer, Defer, DEFER!
     ‣ Use validation methods correctly
     ‣ Remember the elastic racetrack
References
    ‣   Ely Green eld: “Building a Flex Component”
        •   http://www.on ex.org/ACDS/
            BuildingA...
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Diving Deep with the Flex Component Life Cycle

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Transcript of "Diving Deep with the Flex Component Life Cycle"

  1. 1. Diving Deep with the Flex Component Lifecycle Joshua Jamison EffectiveUI www.effectiveui.com January 30, 2009
  2. 2. Who am I? ‣ Joshua Jamison • Software Architect @ EffectiveUI
  3. 3. Who are you (hopefully)? ‣ Beginner to intermediate level developers ‣ Anyone who doesn’t currently understand the lifecycle ‣ Anyone who wants a good review of the basics
  4. 4. What’s this about, anyway? ‣ Flex component lifecycle ‣ Flex frame cycle (“elastic racetrack”)
  5. 5. Flex Component Lifecycle ‣ What is it? • The way the framework interacts with every Flex component • A set of methods the framework calls to instantiate, control, and destroy components • Methods that make the most of the elastic racetrack
  6. 6. Elastic Racetrack: introduction image courtesy of Ted Patrick ‣ Flex component lifecycle is built on this frame model ‣ More on this later
  7. 7. A frame in AS3 image courtesy of Sean Christmann
  8. 8. Phases of the Lifecycle ‣ 3 Main Phases: ‣ BIRTH: • construction, con guration, attachment, initialization ‣ LIFE: • invalidation, validation, interaction ‣ DEATH: • detachment, garbage collection
  9. 9. Birth Congratulations: You’re about to have a component.
  10. 10. Construction Birth construction con guration attachment initialization Life Death
  11. 11. What is a constructor? ‣ A function called to instantiate (create in memory) a new instance of a class Birth construction con guration attachment initialization Life Death
  12. 12. How is a constructor invoked? Actionscript: var theLabel : Label = new Label(); MXML: <mx:Label id="theLabel"/> Birth construction con guration attachment initialization Life Death
  13. 13. What does a constructor have access to? ‣ Properties on the class ‣ Methods on the class ‣ Children have not yet been created! Birth construction con guration attachment initialization Life Death
  14. 14. What does an ActionScript3 constructor look like? public function ComponentName() { super(); //blah blah blah } ‣ No required arguments (if it will be used in MXML); zero, or all optional ‣ Only one per class (no overloading!) ‣ No return type Birth ‣ Must be public construction con guration ‣ Calls super() to invoke superclass constructor; if attachment initialization you don’t, the compiler will! Life Death
  15. 15. What does an MXML constructor look like? ‣ No need to de ne one. In fact, if you try to put one in an <mx:Script> block, you’ll get an error. ‣ Why? Remember: MXML = Actionscript. A constructor is created by the compiler in the Actionscript generated from the MXML. Birth ‣ Specify “-keep” in the Flex Builder construction con guration compiler arguments and look at the attachment generated code to verify this. initialization Life Death
  16. 16. What should a constructor do? ‣ Not much. Since the component’s children have not yet been created, there’s not much that can be done. ‣ There are speci c methods (such as createChildren) that should be used for most of the things you’d be tempted to put in a constructor. Birth ‣ A good place to add event listeners to the construction con guration object. attachment initialization Life Death
  17. 17. Don’t create or attach children in the constructor ‣ It’s best to delay the cost of createChildren calls for added children until it’s necessary Birth construction con guration attachment initialization Life Death
  18. 18. Con guration Birth construction con guration attachment initialization Life Death
  19. 19. Con guration ‣ The process of assigning values to properties on objects ‣ In MXML, properties are assigned in this phase, before components are attached or initialized <local:SampleChild property1="value!"/> Birth construction con guration attachment initialization Life Death
  20. 20. Hooray: Sample code! <mx:Application ...> ... <local:SampleChild property1="value!"/> </mx:Application> Output: SampleChild constructor Birth SampleChild.property1 setter construction Adding child SampleChild4 con guration attachment initialization Life Death
  21. 21. Con guration and Containers ‣ Containers must not expect their children have to be instantiated when properties are set. <mx:Application ...> <local:SampleContainer property1="value!"> <local:SampleChild property1="value!"/> </local:SampleContainer> </mx:Application> SampleContainer constructor Birth construction SampleContainer.property1 setter con guration SampleChild constructor attachment SampleChild.property1 setter initialization Life Death
  22. 22. Con guration Optimization ‣ To avoid performance bottlenecks, make your setters fast and defer any real work until validation ‣ We’ll talk more about deferment in the validation / invalidation section Birth construction con guration attachment initialization Life Death
  23. 23. Attachment Birth construction con guration attachment initialization Life Death
  24. 24. What is attachment? ‣ Adding a component to the display list (addChild, addChildAt, MXML declaration) ‣ The component lifecycle is stalled after con guration until attachment occurs. Birth construction con guration attachment initialization Life Death
  25. 25. Consider this component: public class A extends UIComponent { public function A() { (It traces all of its methods.) trace( "CONSTRUCTOR" ); super(); } override protected function createChildren() : void { trace( "CREATECHILDREN" ); super.createChildren(); } override protected function measure() : void { trace( "MEASURE" ); super.measure(); } override protected function updateDisplayList(width:Number, height:Number) : void { trace( "UPDATEDISPLAYLIST" ); super.updateDisplayList(width,height); } override protected function commitProperties():void { trace( "COMMITPROPERTIES" ); super.commitProperties(); }
  26. 26. And this application: <mx:Application ...> <mx:Script> <![CDATA[ override protected function createChildren() : void { super.createChildren(); var a : A = new A(); } ]]> </mx:Script> </mx:Application> Output: CONSTRUCTOR ‣ Without attachment, the rest of the lifecycle doesn’t happen.
  27. 27. But what about this application? <mx:Application ...> <mx:Script> <![CDATA[ override protected function createChildren() : void { super.createChildren(); var a : A = new A(); this.addChild( a ); } ]]> </mx:Script> </mx:Application> Output: CONSTRUCTOR CREATECHILDREN COMMITPROPERTIES MEASURE UPDATEDISPLAYLIST ‣ Moral of the story: don’t add components to the stage until you need them.
  28. 28. Initialization Birth construction con guration attachment initialization Life Death
  29. 29. Initialization ‣ 2 phases, 3 events: 1. ‘preInitialize’ dispatched Create 2. createChildren(); called 3. ‘initialize’ dispatched Validate 4. rst validation pass occurs 5. ‘creationComplete’ dispatched Birth construction con guration attachment initialization Life Death
  30. 30. createChildren() ‣ MXML uses the createChildren() method to add children to containers ‣ Override this method to add children using AS • Follow MXML’s creation strategy: create, con gure, attach override protected function createChildren():void { ... create textField = new UITextField(); textField.enabled = enabled; con gure textField.ignorePadding = true; textField.addEventListener("textFieldStyleChange", textField_textFieldStyleChangeHandler); ... ... attach } addChild(DisplayObject(textField));
  31. 31. rst validation pass ‣ Invalidation is not part of initialization - only Validation ‣ Validation consists of 3 methods: • commitProperties() • measure() • updateDisplayList() ‣ more on these later Birth construction con guration attachment initialization Life Death
  32. 32. Life They grow up so fast.
  33. 33. Invalidation Birth Life invalidation validation interaction Death
  34. 34. Invalidation / Validation cycle ‣ Flex imposes deferred validation on the Flash API • goal: defer screen updates until all properties have been set ‣ 3 main method pairs to be aware of: • invalidateProperties() -> commitProperties() • invalidateSize() -> measure() • invalidateDisplayList() -> updateDisplayList()
  35. 35. Invalidation / Validation theory ‣ First, a little theory.
  36. 36. Deferment ‣ Deferment is the central concept to understand in the component Life-cycle ‣ Use private variables and boolean ags to defer setting any render-related properties until the proper validation method
  37. 37. Text-book example Bad: public function set text(value:String):void { myLabel.text = value; // Possible Error! during first config phase, // myLabel might not exist! } Good: private var _text:String = ""; public function set text(value:String):void override protected function { commitProperties():void{ textSet = true; { _text = value; if(textChanged){ textChanged = true; myLabel.text = _text; textChanged = false; invalidateProperties(); } invalidateSize(); super.commitProperties(); invalidateDisplayList(); } }
  38. 38. The Elastic Racetrack revisited image courtesy of Sean Christmann Invalidation occurs here
  39. 39. Invalidation methods ‣ invalidateProperties() • Any property changes ‣ invalidateSize() • Changes to width or height ‣ invalidateDisplayList() • Changes to child component size or position Birth Life invalidation validation interaction Death
  40. 40. Invalidation example 1 <mx:Application> <mx:Script> <![CDATA[ import mx.collections.ArrayCollection; [Bindable] public var arr : ArrayCollection = new ArrayCollection(); public function onClick() : void { var c : int = 0; while( c++ < 20 ) { arr.addItem( c ); } } ]]> </mx:Script> <mx:VBox> <mx:Button label="Click me!" click="onClick()"/> <test:BadList id="theList" dataProvider="{arr}"/> </mx:VBox> </mx:Application>
  41. 41. Invalidation example 2 public class BadList extends VBox { private var _dataProvider : ArrayCollection; public function set dataProvider( arr : ArrayCollection ) : void { this._dataProvider = arr; arr.addEventListener( CollectionEvent.COLLECTION_CHANGE, dataProviderChangeHandler ); } private function dataProviderChangeHandler( e : Event ) : void { this.removeAllChildren(); for each( var n : Number in this._dataProvider ) { var l : Label = new Label(); l.text = n.toString(); this.addChild( l ); } } public function BadList() {} } Result: dataProviderChangeHandler called 20 times
  42. 42. Invalidation example 3 public class GoodList extends VBox { private var _dataProvider : ArrayCollection; private var _dataProviderChanged : Boolean = false; public function set dataProvider( arr : ArrayCollection ) : void { this._dataProvider = arr; arr.addEventListener( CollectionEvent.COLLECTION_CHANGE, dataProviderChangeHandler ); this._dataProviderChanged = true; this.invalidateProperties(); } override protected function commitProperties():void { super.commitProperties(); if( this._dataProviderChanged ) { this.removeAllChildren(); for each( var n : Number in this._dataProvider ) { var l : Label = new Label(); l.text = n.toString(); Result: commitProperties this.addChild( l ); called only twice (once } this._dataProviderChanged = false; during initialization) } } private function dataProviderChangeHandler( e : Event ) : void { this._dataProviderChanged = true; this.invalidateProperties(); } public function GoodList() {} }
  43. 43. Validation Birth Life invalidation validation interaction Death
  44. 44. The Elastic Racetrack revisited Validation occurs here
  45. 45. Validation ‣ Apply the changes deferred during invalidation ‣ Update all visual aspects of the application in preparation for the render phase ‣ 3 methods: • commitProperties() • measure() Birth Life • updateDisplayList() invalidation validation interaction Death
  46. 46. commitProperties() ‣ Ely says: “Calculate and commit the effects of changes to properties and underlying data.” ‣ Invoked rst - immediately before measurement and layout Birth Life invalidation validation interaction Death
  47. 47. commitProperties() cont. ‣ ALL changes based on property and data events go here ‣ Even creating and destroying children, so long as they’re based on changes to properties or underlying data ‣ Example: any list based component with empty renderers on the screen Birth Life invalidation validation interaction Death
  48. 48. measure() ‣ Component calculates its preferred (“default”) and minimum proportions based on content, layout rules, constraints. ‣ Measure is called bottom up - lowest children rst ‣ Caused by “invalidateSize()” ‣ NEVER called for explicitly sized Birth Life components invalidation validation interaction Death
  49. 49. overriding measure() ‣ Used for dynamic layout containers (VBox, etc.) ‣ Use getExplicitOrMeasuredWidth() (or height) to get child proportions ‣ ALWAYS called during initialization ‣ Call super.measure() rst! ‣ Set measuredHeight, measuredWidth for Birth the default values; measuredMinHeight Life invalidation and measuredMinWidth for the minimum. validation interaction Death
  50. 50. measure() cont. ‣ Not reliable - Framework optimizes away any calls to measure it deems “unecessary” Birth Life invalidation validation interaction Death
  51. 51. updateDisplayList() ‣ All drawing and layout code goes here, making this the core method for all container objects ‣ Caused by invalidateDisplayList(); ‣ Concerned with repositioning and resizing children ‣ updateDisplayList() is called top-down Birth Life invalidation validation interaction Death
  52. 52. Overriding updateDisplayList() ‣ Usually call super.updateDisplayList() rst • super() is optional - don’t call it if you’re overriding everything it does ‣ Size and lay out children using move(x,y) and setActualSize(w,h) if possible • I never have good luck with setActualSize() Birth Life invalidation validation interaction Death
  53. 53. Elastic Racetrack cont. ‣ User Actions • Dispatch invalidation events • Interact with any non-validation events from this frame (mouse movements, timers, etc.)
  54. 54. Elastic Racetrack Cont. ‣ Invalidate Action • Process all validation calls ‣ Render Action • Do the heavy lifting - actually draw on the screen
  55. 55. The Elastic Racetrack revisited Queued Invalidation Deferred Validation Render!
  56. 56. Interaction Birth Life invalidation validation interaction Death
  57. 57. How do objects know when something happens? ‣ Events: objects passed around when anything interesting goes on (clicks, moves, changes, timers...) ‣ If something happens to a component, it “ res” or “dispatches” the event ‣ If another component wants to know when something happens, it “listens” for events Birth Life ‣ Event-based architecture is loosely- invalidation validation coupled interaction Death
  58. 58. Bene ts of Loosely-Coupled Architectures ‣ Everything becomes more reusable ‣ Components don’t have to know anything about the components in which they’re used Birth Life invalidation validation interaction Death
  59. 59. Who can dispatch events? ‣ Subclasses of EventDispatcher • EventDispatcher inherits directly from Object ‣ Simply call dispatchEvent(event) to re off an event when something happens Birth Life invalidation validation interaction Death
  60. 60. How to tell events apart? ‣ Event class • Different classes allow for customized payloads ‣ “type” eld: a constant Birth Life invalidation validation interaction Death
  61. 61. Common Events ‣ Event.CHANGE ‣ MouseEvent.CLICK ‣ FlexEvent.CREATION_COMPLETE ‣ Event.RESIZE ‣ MouseEvent.ROLL_OUT Birth Life invalidation validation interaction Death
  62. 62. Handling Events ‣ <mx:Button id=”theButton” click=”callThisFunction(event)”/> ‣ theButton.addEventListener( MouseEvent .CLICK, callThisFunction ) Birth Life invalidation validation interaction Death
  63. 63. Event Propagation ‣ Three phases: Capturing, Targeting, Bubbling Application Application Capturing Bubbling Phase Phase Target Targeting Birth Phase Life invalidation validation interaction Death
  64. 64. Event Propagation ‣ Three phases: Capturing, Targeting, Bubbling <mx:Application initialize="onInitialize()"> <mx:Script> <![CDATA[ public function onInitialize() : void { this.addEventListener( MouseEvent.CLICK, clickHandler, true ); this.addEventListener( MouseEvent.CLICK, clickHandler, false ); outer.addEventListener( MouseEvent.CLICK, clickHandler, true ); outer.addEventListener( MouseEvent.CLICK, clickHandler, false ); inner.addEventListener( MouseEvent.CLICK, clickHandler, true ); inner.addEventListener( MouseEvent.CLICK, clickHandler, false ); button.addEventListener( MouseEvent.CLICK, clickHandler, true ); button.addEventListener( MouseEvent.CLICK, clickHandler, false ); } public function clickHandler( e : Event ) : void { trace("----------------------------------------------------------"); trace("TARGET: " + e.target.id ); trace("CURRENT TARGET: " + e.currentTarget.id ); trace("PHASE: " + ( e.eventPhase == 1 ? "CAPTURE" : ( e.eventPhase == 2 ? "TARGET" : "BUBBLE" ) ) ); } ]]> </mx:Script> <mx:VBox> <mx:Panel id="outer"> <mx:TitleWindow id="inner"> <mx:Button id="button"/> </mx:TitleWindow> Birth </mx:Panel> </mx:VBox> Life </mx:Application> invalidation ‣ validation interaction Death
  65. 65. Event Propagation ---------------------------------------------------------- TARGET: button CURRENT TARGET: eventTest PHASE: CAPTURE ---------------------------------------------------------- TARGET: button CURRENT TARGET: outer PHASE: CAPTURE ---------------------------------------------------------- TARGET: button CURRENT TARGET: inner PHASE: CAPTURE ---------------------------------------------------------- TARGET: button CURRENT TARGET: button PHASE: TARGET ---------------------------------------------------------- TARGET: button CURRENT TARGET: inner PHASE: BUBBLE ---------------------------------------------------------- TARGET: button CURRENT TARGET: outer PHASE: BUBBLE ---------------------------------------------------------- Birth TARGET: button CURRENT TARGET: eventTest Life PHASE: BUBBLE invalidation validation interaction Death
  66. 66. Stopping events from propagating ‣ stopPropagation() : Prevents processing of any event listeners in nodes subsequent to the current node in the event ow ‣ stopImmediatePropagation() : Prevents processing of any event listeners in the current node and any subsequent nodes in the event ow Birth Life invalidation validation interaction Death
  67. 67. target vs. currentTarget ‣ target: the object that dispatched the event (doesn’t change) ‣ currentTarget: the object who is currently being checked for speci c event listeners (changes) Birth Life invalidation validation interaction Death
  68. 68. Dispatching events from custom components ‣ MXML: <mx:Metadata> [Event(name="atePizza", type="flash.events.JoshEvent")] </mx:Metadata> ‣ Actionscript: [Event(name="atePizza", type="flash.events.JoshEvent")] public class MyComponent extends UIComponent { ... } Birth Life invalidation validation interaction Death
  69. 69. Death All good things come to an end.
  70. 70. Detachment Birth Life Death detachment garbage collection
  71. 71. Detachment ‣ “Detachment” refers to the process of removing a child from the display list ‣ These children can be re-parented (brought back to life) or abandoned to die ‣ Abandoned components don’t get validation calls and aren’t drawn ‣ If an abandoned component has no more Birth active references, it *should* be garbage- Life Death collected detachment garbage collection
  72. 72. Detachment cont. ‣ Re-parenting isn’t cheap, but it’s cheaper than re-creating the same component twice ‣ Children do not need to be removed from their parent before being re-parented, but always should be ‣ Consider hiding rather than removing • set visible and includeInLayout to false Birth Life Death detachment garbage collection
  73. 73. Garbage Collection Birth Life Death detachment garbage collection
  74. 74. Garbage Collection ‣ The process by which memory is returned to the system ‣ Only objects with no remaining references to them will be gc’d • Set references to detached children to “null” to mark them for GC ‣ Talk to Grant Skinner about forcing GC Birth • http://gskinner.com/blog/archives/2006/08/as3_resource_ma_2.html Life Death detachment garbage collection
  75. 75. Conclusion ‣ Defer, Defer, DEFER! ‣ Use validation methods correctly ‣ Remember the elastic racetrack
  76. 76. References ‣ Ely Green eld: “Building a Flex Component” • http://www.on ex.org/ACDS/ BuildingAFlexComponent.pdf ‣ Cha c Kazoun, Joey Lott: “Programming Flex 2” by O’Reilly • http://oreilly.com/catalog/9780596526894/ ‣ Colin Moock: “Essential Actionscript 3.0” by O’Reilly • http://oreilly.com/catalog/9780596526948/ index.html
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