The implementation of this history class is also simple. The example above uses two navigation components. The following is the class code for those two components:

// SiteNavigation.as
class SiteNavigation extends MovieClip {
private var buttonOne:MovieClip;
private var buttonTwo:MovieClip;
private var buttonThree:MovieClip;
private var buttonFour:MovieClip;
private var history:History;
function SiteNavigation() {
history = History.getInstance();
buttonOne.onRelease = function() {
if(this._parent.history.addItem('One')) {
this._parent._parent.gotoAndPlay('One');
}
buttonTwo.onRelease = function() {
if(this._parent.history.addItem('Two')) {
this._parent._parent.gotoAndPlay('Two');
}
buttonThree.onRelease = function() {
if(this._parent.history.addItem('Three')) {
this._parent._parent.gotoAndPlay('Three');
}
buttonFour.onRelease = function() {
if(this._parent.history.addItem('Four')) {
this._parent._parent.gotoAndPlay('Four');
}
// HistoryNavigation.as
class HistoryNavigation extends MovieClip {
private var backButton:MovieClip;
private var forwardButton:MovieClip;
private var history:History;
function HistoryNavigation() {
history = History.getInstance();
backButton.onRelease = function() {
this._parent._parent.gotoAndPlay
(this._parent.history.previousItem);
}
forwardButton.onRelease = function() {
this._parent._parent.gotoAndPlay
(this._parent.history.nextItem);
}

Conclusion
The Singleton pattern is both a simple and proven design pattern for restricting instantiation and for providing a global access point. A variation of this class is the Multiton pattern, which also restricts instantiation, but allows for a fixed number of instances.

This article was originally published on Community MX (www.communitymx.com).