Observer Pattern
function Subject(){
this.observers = new ObserverList();
}
Subject.prototype.addObserver = function( observer ){
this.observers.add( observer );
};
Subject.prototype.removeObserver = function( observer ){
this.observers.removeAt( this.observers.indexOf( observer, 0 ) );
};
Subject.prototype.notify = function( context ){
var observerCount = this.observers.count();
for(var i=0; i < observerCount; i++){
this.observers.get(i).update( context ); // update method is implemented in all the observer
}
};
function ObserverList(){
this.observerList = [];
}
ObserverList.prototype.count = function(){
return this.observerList.length;
};
ObserverList.prototype.add = function( obj ){
return this.observerList.push( obj );
};
ObserverList.prototype.get = function( index ){
if( index > -1 && index < this.observerList.length ){
return this.observerList[ index ];
}
};
ObserverList.prototype.indexOf = function( obj, startIndex ){
var i = startIndex;
while( i < this.observerList.length ){
if( this.observerList[i] === obj ){
return i;
}
i++;
}
return -1;
};
ObserverList.prototype.removeAt = function( index ){
this.observerList.splice( index, 1 );
};
// skeleton
function Observer(){
this.update = function(){
// ...
};
}
// every observer must have an update method, so that it can do things once notified