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MyClass

Chapter 20

As you can see, the

class

keyword is used to define

MyClass

. There is one private variable named

color

, one constructor, and one public method named

sayColor()

. In ECMAScript Edition 4, both

public

and

private

are considered

namespaces

that define the context in which variables and methods

can be accessed. Classes defined in this manner are instantiated in the same way as in ECMAScript

Edition 3, by using the

new

keyword:

var myObject : MyClass = new MyClass();

Along with variables and methods, it is possible to define getters and setters for properties. The getter is

called when the variable is used for the value it contains, whereas a setter assigns a new value to a given

variable.

class MyClass {

private var color : String = “red”;

public function get myColor () {

return this.color;

}

public function set myColor (value : String) : Void {

this.color = value;

}

The previous code creates a property named

myColor

, which can be used just like a regular property

(such as

color

), but whose behavior is defined by the getter and setter functions. For instance:

var myObject : MyClass = new MyClass();

myObject.myColor = “blue”;

Typically, this would be done when you want to perform some other action after a property value

changes (such as changing the color of a UI element when the

myColor

property changes).

It is also possible to redefine the behavior of operators when they interact with classes. In ECMAScript

Edition 3, all operators use an object’s

valueOf()

toString()

method, but here it is possible for you

to define exactly how a plus or minus should be used with an instance of a particular class.

class MyClass {

private var value : Integer = 25;

public function MyClass(value : Integer) {

this.value = value;

}

public function getValue() : Integer {

return this.value;

}

operator function “+” (anotherObject : MyClass) : MyClass {

return new MyClass(this.value + anotherObject.getValue());

}

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