MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manuel d'utilisateur télécharger pdf (Page 33)

Typing 33

Type detection

To perform type detection, you should use is rather than typeof or instanceof. The is

function examines types, whereas the

instanceof function looks at the prototype chain. The

instanceof function has been deprecated.

For example:

class B {

public function B() {}

}

class A extends B {

public function A() {

super();

}

class Main extends MovieClip {

public function Main() {

var a:A = new A();

trace(a instanceof B); // false; instanceof is deprecated.

trace(a instanceof A); // false; instanceof is deprecated.

trace(a is B); // true

trace(a is A); // true

}

Primitive types

In ActionScript 3.0, there is no longer a distinction between primitive types such as strings

and instances of the String class. All strings are instances of String; every datatype is an

instance of some class. The same is true for numbers and Booleans. For example:

print("test" == String("test")); // true

print("test" === String("test")); // true

print(45 == new Number(45)); // true

print(45 === new Number(45)); // true

print("one;two;three".substring(4,7)); // "two"

print((255).toString(16)); // "ff"

Non-assignment expressions

A non-assignment expression is any expression where a value is not assigned to a property (or

a variable or argument); for example:

var myVar : hintString ? String : Number;

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MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manuel d'utilisateur Page 33