object-oriented actionscript 3.0

4th-6th June 2008Edinburgh, Scotland

Object-Oriented ActionScript 3.0

Peter Elst


Object-Oriented Programming

■ Difficult■ Scary■ Overhead■ Only for large teams



■ Difficult? Structured code■ Scary■ Overhead■ Only for large teams



■ Difficult? Structured code■ Scary? Initial learning curve■ Overhead■ Only for large teams



■ Difficult? Structured code■ Scary? Initial learning curve■ Overhead? Promotes code reuse■ Only for large teams



■ Difficult? Structured code■ Scary? Initial learning curve■ Overhead? Promotes code reuse■ Only for large teams? Useful for anyone


Classes (the artist formerly known as prototype)

■ The way things were:

function Conference() { this.name = "Flashforward";}

Conference.prototype.getName = function() { trace("conference name: "+this.name);}

var myConference = new Conference();myConference.getName();


Classes (the artist formerly known as prototype)

■ The way things are:

package { public class Conference { public var name:String = "Flashforward";

public function getName():void { trace("conference name: "+this.name); } }}


Instances

■ Classes provide a blueprint■ Instances set their values for properties


Inheritance (getting rich the easy way)

■ Classes can extend each-other■ Avoids code duplication■ Properties and methods can be overridden

package { public class SuperClass extends BaseClass { public function SuperClass() { super(); } }}


Inheritance vs composition

■ Inheritance deals with an is a relationship■ Composition is used for has a relationships

Employee is a Person Employee has a Job


Encapsulation (don't touch my stuff)

■ Protect the inner workings of your code through the use of access modifiers

■ Provide an API for other classes to use by providing getter/setter methods

public - anything can access this private - only the class itself can access protected - class and its subclasses can access internal (default) - all classes in the same class package


Polymorphism (copycat behavior)

■ Have classes use the same method names ■ Allows classes to be swapped at runtime■ Same name but different implementation

Doctor.work() Fireman.work() WebDeveloper.work()


Interfaces (sign on the dotted line)

■ Classes can use one or more interfaces ■ Interfaces require a class to implement a

specific set of methods■ Used to formalize polymorphism■ Interfaces can extend each-other


Design PatternsGeneral solutions to common problems


Observer pattern

■ Problem: notify other classes when an update occurs in a data model

■ Solution: keep an array of all instances that want to be notified and call their update method then the model has changed


Singleton pattern

■ Problem: allow only one instance of a class to exist in an application

■ Solution: prevent the constructor from being called outside of the class scope and provide a static method for returning the single class instance


Want to learn more?

Books■ Object-Oriented ActionScript 3.0■ Essential ActionScript 3.0

Course■ Core ActionScript 3.0 (Skills Matter - London)


Thanks!


Get in touch!

Peter ElstFlash Platform Consultant

Blog: www.peterelst.comEmail: [email protected]: www.linkedin.com/in/peterelstTwitter: www.twitter.com/peterelst

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