Brief Introduction to OOP


Object-oriented programming (OOP) is sometimes shrouded in mystery and mysticism. You might have encountered phrases such as "the zen of OOP." But when you get right down to it, OOP is just a way of organizing code. I'd even go so far as to say that it's the best way to organize complex or large projects.

Chapter 11, "Introducing ActionScript," covered simple datatypes in Flash. Variables are containers, and datatypes are a way to say what kind of data can be stored in that container. A variable with a number datatype holds a number, a string holds a string of characters, and an array holds a list of strings, numbers, or objects.

Each datatype has certain properties and methods unique to its type. For example, a number can hold numerical values and have mathematical methods applied to it. A class defines a datatype.

When we start discussing objects, things start getting more interesting. An object can hold properties, which are simply variables of a datatype (the object container holds the variable container). Objects can also hold another complex datatype called functions. In Chapter 11, functions were defined as encapsulated segments of code with a single set of functionality. They are "run" when called by name in another section of code. When functions are stored in an object, they are called methods.

Classes

So how do you organize code differently when you work with ActionScript 2.0 and object-oriented programming in Flash? When Chapter 11 introduced ActionScripting, you learned to look at variables and functions as ways to organize your code. Now you're ready to move to a more sophisticated organizational structure where all of your code is stored in objects, which are simply containers of containers.

However, before you can create an instance of an object, you must have a class. A class describes an object as well as what properties and methods belong to that object. It can be one of the built-in classes, such as Math, or a custom class that you write yourself. In either case, a class is a datatype that describes all the properties and methods that are available to be applied to an object created from the class description.

You can think of a class as the blueprint for an object. Just as many buildings can be constructed from the same set of blueprints, multiple objects can be described by a single class. It is important to understand that all datatypes and objects in Flash are class-based. The MovieClip object, Date object, Array object, Math object, and even the Object object are all based on classes that are built into Flash. For a complete list of all built-in datatypes (classes) available to you in Flash, go to the Action panel and choose Types from the left Action listing.



Special Edition Using Macromedia Studio 8
Special Edition Using Macromedia Studio 8
ISBN: 0789733854
EAN: 2147483647
Year: 2003
Pages: 337

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net