topical media & game development

topical media & game development

[] readme course(s) preface I 1 2 II 3 4 III 5 6 7 IV 8 9 10 V 11 12 afterthought(s) appendix reference(s) example(s) resource(s) _

actionscript-lib-util-Observable.ax

actionscript-lib-util-Observable.ax [swf] flex


  package  {
    //  import util.Observer;

A Java-style @ax-actionscript-lib-util-Observable class used to represent the "subject" of the Observer design pattern. Observers must implement the Observer interface, and register to observe the subject via addObserver().


  
    public class @ax-actionscript-lib-util-Observable {
      // A flag indicating whether this object has changed.
      private var changed:Boolean = false;
      // A list of observers.
      private var observers:Array;

Constructor function.


  
      public function @ax-actionscript-lib-util-Observable () {
        observers = new Array();
      }

Adds an observer to the list of observers.
parameter: o The observer to be added.


  
      public function addObserver (o:actionscript_lib_util_Observer):Boolean {
        // Can't add a null observer.
        if (o == null) {
          return false;
        }
  
        // Don't add an observer more than once.
        for (var i:Number = 0; i < observers.length; i++) {
          if (observers[i] == o) {
            // The observer is already observing, so quit.
            return false;
          }
       }
  
        // Put the observer into the list.
        observers.push(o);
        return true;
      }

Removes an observer from the list of observers.
parameter: o The observer to remove.


  
      public function removeObserver (o:actionscript_lib_util_Observer):Boolean {
        // Find and remove the observer.
        var len:Number = observers.length;
        for (var i:Number = 0; i < len; i++) {
          if (observers[i] == o) {
            observers.splice(i, 1);
            return true;
          }
        }
        return false;
      }

Tell all observers that the subject has changed.
parameter: infoObj An object containing arbitrary data to pass to observers.


  
      public function notifyObservers (infoObj:Object):void {
        // If the object hasn't changed, don't bother notifying observers.
        if (!changed) {
          return;
        }
  
        // Make a copy of the observers array. We do this
        // so that we can be sure the list won't change while
        // we're processing it.
        var observersSnapshot:Array = observers.slice(0);
  
        // This change has been processed, so unset the "changed" flag.
        clearChanged();
  
        // Invoke update() on all observers.
        for (var i:Number = observersSnapshot.length-1; i >= 0; i--) {
          observersSnapshot[i].update(this, infoObj);
        }
      }

Removes all observers from the observer list.


  
      public function clearObservers ():void {
       observers = new Array();
      }

Indicates that the subject has changed.


  
      protected function setChanged():void {
        changed = true;
      }

Indicates that the subject has either not changed or has notified its observers of the most recent change.


  
      protected function clearChanged ():void {
        changed = false;
      }

Checks if the subject has changed.
returns: true if the subject has changed, as determined by setChanged().


  
      public function hasChanged():Boolean {
        return changed;
      }

Returns the number of observers in the observer list.
returns: An integer: the number of observers for this subject.


  
      public function countObservers ():Number {
        return observers.length;
      }
    }
  }

[] readme course(s) preface I 1 2 II 3 4 III 5 6 7 IV 8 9 10 V 11 12 afterthought(s) appendix reference(s) example(s) resource(s) _

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