Statements, Keywords & Directives 

function functionName(parameter0, parameter1, ...rest){ 
	// statement(s) 
} 

Specifies that a function will accept any number of comma-delimited arguments. The list of arguments becomes an array that is available throughout the function body. The name of the array is specified after the ... characters in the parameter declaration. The parameter can have any name that is not a reserved word.

If used with other parameters, the ... (rest) parameter declaration must be the last parameter specified. The ... (rest) parameter array is populated only if the number of arguments passed to the function exceeds the number of other parameters.

Each argument in the comma-delimited list of arguments is placed into an element of the array. If you pass an instance of the Array class, the entire array is placed into a single element of the ... (rest) parameter array.

Use of this parameter makes the arguments object unavailable. Although the ... (rest) parameter gives you the same functionality as the arguments array and arguments.length property, it does not provide functionality similar to that provided by arguments.callee. Make sure you do not need to use arguments.callee before using the ... (rest) parameter.

package {
	import flash.display.MovieClip;
	
	public class RestParamExample extends MovieClip {
		public function RestParamExample() {
			traceParams(100, 130, "two"); // 100,130,two
			trace(average(4, 7, 13));     // 8
		}
	}
}


function traceParams(... rest) {
 	trace(rest);
 }
 
function average(... args) : Number{
	var sum:Number = 0;
	for (var i:uint = 0; i < args.length; i++) {
		sum += args[i];
	}
	return (sum / args.length);
}

Related API Elements

Defines methods and properties of the core ActionScript classes that are fixed properties instead of prototype properties. When you set the "-as3" compiler option to true (which is the default setting in Flex Builder 2), the AS3 namespace is automatically opened for all the core classes. This means that an instance of a core class will use fixed properties and methods instead of the versions of those same properties and methods that are attached to the class's prototype object. The use of fixed properties usually provides better performance, but at the cost of backward compatibility with the ECMAScript edition 3 language specification (ECMA-262).

Related API Elements

Appears within a loop (for, for..in, for each..in, do..while, or while) or within a block of statements associated with a particular case in a switch statement. When used in a loop, the break statement instructs Flash to skip the rest of the loop body, stop the looping action, and execute the statement following the loop statement. When used in a switch, the break statement instructs Flash to skip the rest of the statements in that case block and jump to the first statement that follows the enclosing switch statement.

In nested loops, break only skips the rest of the immediate loop and does not break out of the entire series of nested loops. To break out of an entire series of nested loops, use label or try..catch..finally.

The break statement can have an optional label that must match an outer labeled statement. Use of a label that does not match the label of an outer statement is a syntax error. Labeled break statements can be used to break out of multiple levels of nested loop statements, switch statements, or block statements. For an example, see the entry for the label statement.

var i:int = 0;
while (true) { 
	trace(i); 
	if (i >= 10) { 
		break; // this will terminate/exit the loop 
	} 
	i++; 
} 
/*
0 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10*/

Related API Elements

case jumpTarget: statements

Defines a jump target for the switch statement. If the jumpTarget parameter equals the expression parameter of the switch statement using strict equality (===), Flash Player executes the statements in the statements parameter until it encounters a break statement or the end of the switch statement.

If you use the case statement outside a switch statement, it produces an error and the script doesn't compile.

var thisMonth:int = new Date().getMonth(); 
switch (thisMonth) { 
	case 0 : 
		trace("January"); 
		break; 
	case 1 : 
		trace("February"); 
		break; 
	case 5 : 
	case 6 : 
	case 7 : 
		trace("Some summer month"); 
		break; 
	case 8 : 
		trace("September"); 
		break; 
	default : 
		trace("some other month"); 
}

Related API Elements

[dynamic] [public | internal] [final] class className [ extends superClass ] [ implements interfaceName[, interfaceName... ] ] { 
	// class definition here
}

Defines a class, which lets you instantiate objects that share methods and properties that you define. For example, if you are developing an invoice-tracking system, you could create an Invoice class that defines all the methods and properties that each invoice should have. You would then use the new Invoice() command to create Invoice objects.

Each ActionScript source file can contain only one class that is visible to other source files or scripts. The externally visible class can be a public or internal class, and must be defined inside a package statement. If you include other classes in the same file, the classes must be placed outside of the package statement and at the end of the file.

The name of the externally visible class must match the name of the ActionScript source file that contains the class. The name of the source file must be the name of the class with the file extension .as appended. For example, if you name a class Student, the file that defines the class must be named Student.as.

You cannot nest class definitions; that is, you cannot define additional classes within a class definition.

You can define a constructor method, which is a method that is executed whenever a new instance of the class is created. The name of the constructor method must match the name of the class. If you do not define a constructor method, a default constructor is created for you.

To indicate that objects can add and access dynamic properties at runtime, precede the class statement with the dynamic keyword. To declare that a class implements an interface, use the implements keyword. To create subclasses of a class, use the extends keyword. (A class can extend only one class, but can implement several interfaces.) You can use implements and extends in a single statement. The following examples show typical uses of the implements and extends keywords:

class C implements Interface_i, Interface_j // OK 
class C extends Class_d implements Interface_i, Interface_j // OK 
class C extends Class_d, Class_e // not OK 

// Filename Plant.as 
package {
  public class Plant { 
	// Define property names and types 
	private var _leafType:String; 
	private var _bloomSeason:String; 
	// Following line is constructor 
	// because it has the same name as the class 
	public function Plant(param_leafType:String, param_bloomSeason:String) { 
		// Assign passed values to properties when new Plant object is created 
		_leafType = param_leafType; 
		_bloomSeason = param_bloomSeason; 
	} 
	// Create methods to return property values, because best practice 
	// recommends against directly referencing a property of a class 
	public function get leafType():String { 
		return _leafType; 
	} 
	public function get bloomSeason():String { 
		return _bloomSeason; 
	} 
  }
}

var pineTree:Plant = new Plant("Evergreen", "N/A"); 
// Confirm parameters were passed correctly 
trace(pineTree.leafType); 
trace(pineTree.bloomSeason); 

Related API Elements

const identifier = value 

Specifies a constant, which is a variable that can be assigned a value only once.

You can strictly type a constant by appending a colon (:) character followed by the data type.

const MIN_AGE:int = 21;
MIN_AGE = 18; // error

const product_array:Array = new Array("Studio", "Dreamweaver", "Flash", "ColdFusion", "Contribute", "Breeze"); 
product_array.push("Flex"); // array operations are allowed
product_array = ["Other"];  // assignment is an error
trace(product_array); 

Related API Elements

continue [label]

Jumps past all remaining statements in the innermost loop and starts the next iteration of the loop as if control had passed to the end of the loop normally. The continue statement has no effect outside a loop. In nested loops, use the optional label parameter to skip more than just the innermost loop.

The continue statement can have an optional label that must match an outer labeled statement. Use of a label that does not match the label of an outer statement is a syntax error. Labeled continue statements can be used to skip multiple levels of nested loop statements.

var i:int = 0; 
while (i < 10) { 
	if (i % 3 == 0) { 
		i++; 
		continue; 
	} 
	trace(i); 
	i++; 
}

 
for (var i:int = 0; i < 10; i++) { 
	if (i % 3 == 0) { 
		continue; 
	} 
	trace(i); 
}

Related API Elements

default: statements 

Defines the default case for a switch statement. The statements execute if the expression parameter of the switch statement doesn't equal (using the strict equality [===] operation) any of the expression parameters that follow the case keywords for a given switch statement.

A switch statement does not require a default case statement. A default case statement does not have to be last in the list. If you use a default statement outside a switch statement, it produces an error and the script doesn't compile.

var dayOfWeek:int = new Date().getDay(); 
switch (dayOfWeek) { 
	case 1 : 
		trace("Monday"); 
		break; 
	case 2 : 
		trace("Tuesday"); 
		break; 
	case 3 : 
		trace("Wednesday"); 
		break; 
	case 4 : 
		trace("Thursday"); 
		break; 
	case 5 : 
		trace("Friday"); 
		break; 
	default : 
		trace("Weekend"); 
}

Related API Elements

The default xml namespace directive sets the default namespace to use for XML objects.

If you do not set default xml namespace, the default namespace is the unnamed namespace (with the URI set to an empty string). The scope of a default xml namespace declaration is within a function block, like the scope of a variable.

var nsDefault1:Namespace = new Namespace("http://www.example.com/namespaces/");
default xml namespace = nsDefault1;
	    
var x1:XML = ;
trace("x1 ns: " + x1.namespace());
			
scopeCheck();	

var x2:XML = ;
trace("x2 ns: " + x2.namespace());
		
function scopeCheck(): void {
	
	var x3:XML = ;
	trace("x3 ns: " + x3.namespace());
				
	var nsDefault2:Namespace = new Namespace("http://schemas.xmlsoap.org/soap/envelope/");
	default xml namespace = nsDefault2;
		    
	var x4:XML = ;
	trace("x4 ns: " + x4.namespace());

}

var nsDefault:Namespace = new Namespace("http://www.example.com/namespaces/");
default xml namespace = nsDefault;
            
var x1:XML = ;

trace(x1.namespace());
	// http://www.example.com/namespaces/

var x2:XML = ;
trace(x2.namespace());
	// http://www.w3.org/1999/XSL/Transform/

var x3:XML = ;
trace(x3.namespace());
	// http://www.example.com/namespaces/

Related API Elements

do { statement(s) } while (condition)

Similar to a while loop, except that the statements are executed once before the initial evaluation of the condition. Subsequently, the statements are executed only if the condition evaluates to true.

A do..while loop ensures that the code inside the loop executes at least once. Although you can also do this with a while loop by placing a copy of the statements to be executed before the while loop begins, many programmers believe that do..while loops are easier to read.

If the condition always evaluates to true, the do..while loop is infinite. If you enter an infinite loop, you encounter problems with Flash Player and eventually get a warning message or crash the player. Whenever possible, use a for loop if you know the number of times you want to loop. Although for loops are easy to read and debug, they cannot replace do..while loops in all circumstances.

var myVar:Number = 0; 
do { 
	trace(myVar); 
	myVar++; 
} 
while (myVar < 5); 
/*
0 
1 
2 
3 
4
*/

Related API Elements

dynamic class className { // class definition here }

Specifies that instances of a class may possess dynamic properties added at runtime. If you use the dynamic attribute on a class, you can add properties to instances of that class at runtime. Classes that are not marked as dynamic are considered sealed, which means that properties cannot be added to instances of the class.

If a class is sealed (not dynamic), attempts to get or set properties on class instances result in an error. If you have your compiler set to strict mode and you specify the data type when you create instances, attempts to add properties to sealed objects generate a compiler error; otherwise, a runtime error occurs.

The dynamic attribute is not inherited by subclasses. If you extend a dynamic class, the subclass is dynamic only if you declare the subclass with the dynamic attribute.

package {

	dynamic class Expando  {
	}
	
	class Sealed {
	}
}

var myExpando:Expando = new Expando();
myExpando.prop1 = "new";
trace(myExpando.prop1); // new

var mySealed:Sealed = new Sealed();
mySealed.prop1 = "newer"; // error

Related API Elements

if (condition) { 
	// statement(s)
} 
else {
	// statement(s)
}

Specifies the statements to run if the condition in the if statement returns false. The curly braces ({}) that enclose the statements to be executed by the else statement are not necessary if only one statement will execute.

if (age_txt.text>=18) { 
	trace("welcome, user"); 
} 
else { 
	trace("sorry, junior"); 
	userObject.minor = true; 
	userObject.accessAllowed = false;
}

if (age_txt.text>18) { 
	trace("welcome, user");
} 
else trace("sorry, junior");

if (score_txt.text>90) { 
	trace("A"); 
} 
else if (score_txt.text>75) { 
	trace("B"); 
} 
else if (score_txt.text>60) { 
	trace("C"); 
} 
else { 
	trace("F"); 
}

Related API Elements

class className extends otherClassName {}
interface interfaceName extends otherInterfaceName {} 

Defines a class that is a subclass of another class. The subclass inherits all the methods, properties, functions, and so on that are defined in the superclass. Classes that are marked as final cannot be extended.

You can also use the extends keyword to extend an interface. An interface that extends another interface includes all the original interface's method declarations.

package {
	class Vehicle { 
	    var numDoors:Number; 
	    var color:String; 
	    public function Vehicle(param_numDoors:Number = 2, param_color:String = null) { 
	        numDoors = param_numDoors; 
	        color = param_color; 
	    } 
	    public function start():void { 
	        trace("[Vehicle] start"); 
	    } 
	    public function stop():void { 
	        trace("[Vehicle] stop"); 
	    } 
	    public function reverse():void { 
	        trace("[Vehicle] reverse"); 
	    } 
	}	
}

package {

	public class Car extends Vehicle { 
	    var fullSizeSpare:Boolean; 
	    public function Car(param_numDoors:Number, param_color:String, param_fullSizeSpare:Boolean) { 
	        numDoors = param_numDoors; 
	        color = param_color; 
	        fullSizeSpare = param_fullSizeSpare; 
	    } 
	    public function activateCarAlarm():void { 
	        trace("[Car] activateCarAlarm"); 
	    } 
	    public override function stop():void { 
	        trace("[Car] stop with antilock brakes"); 
	    } 
	}
}

var myNewCar:Car = new Car(2, "Red", true); 
myNewCar.start(); // [Vehicle] start 
myNewCar.stop(); // [Car] stop with anti-lock brakes 
myNewCar.activateCarAlarm(); // [Car] activateCarAlarm

package {
	class Truck extends Vehicle {
		var numWheels:Number;
		public function Truck(param_numDoors:Number, param_color:String, param_numWheels:Number) { 
			super(param_numDoors, param_color); 
			numWheels = param_numWheels; 
		} 
		public override function reverse():void { 
			beep();
			super.reverse();
		} 
		public function beep():void { 
			trace("[Truck] make beeping sound"); 
		} 
	}
}

var myTruck:Truck = new Truck(2, "White", 18); 
myTruck.reverse(); // [Truck] make beeping sound [Vehicle] reverse 
myTruck.stop(); // [Vehicle] stop

Related API Elements

false

A Boolean value representing false. A Boolean value is either true or false; the opposite of false is true.

When automatic data typing converts false to a number, it becomes 0; when it converts false to a string, it becomes "false".

Note: The string "false" converts to the Boolean value true.

var bool1:Boolean = Boolean(false);

// converts it to the number 0
trace(1 + bool1); // outputs 1

// converts it to a string
trace("String: " + bool1); // outputs String: false

trace(Boolean("false")); // true

if ("false") {
	trace("condition expression evaluated to true");
}
else {
	trace("condition expression evaluated to false");
}
// condition expression evaluated to true

Related API Elements

final function methodName() { 
	// your statements here 
}
final class className {}

Specifies that a method cannot be overridden or that a class cannot be extended. An attempt to override a method, or extend a class, marked as final results in an error.

Related API Elements

Defines methods of the Proxy class. The Proxy class methods are in their own namespace to avoid name conflicts in situations where your Proxy subclass contains instance method names that match any of the Proxy class method names.

Related API Elements

for ([init]; [condition]; [next]) { 
	// statement(s)
}

Evaluates the init (initialize) expression once and then starts a looping sequence. The looping sequence begins by evaluating the condition expression. If the condition expression evaluates to true, statement is executed and next is evaluated. The looping sequence then begins again with the evaluation of the condition expression.

The curly braces ({}) that enclose the block of statements to be executed by the for statement are not necessary if only one statement will execute.

var my_array:Array = new Array(); 
for (var i:Number = 0; i < 10; i++) { 
	my_array[i] = (i + 5) * 10;  
} 
trace(my_array); // 50,60,70,80,90,100,110,120,130,140 

var sum:Number = 0; 
for (var i:Number = 1; i <= 100; i++) { 
	sum += i; 
} 
trace(sum); // 5050

var sum:Number = 0; 
for (var i:Number = 1; i <= 100; i++) 
	sum += i; 
trace(sum); // 5050

Related API Elements

for (variableIterant:String in object){ 
	// statement(s)
} 

Iterates over the dynamic properties of an object or elements in an array and executes statement for each property or element. Object properties are not kept in any particular order, so properties may appear in a seemingly random order. Fixed properties, such as variables and methods defined in a class, are not enumerated by the for..in statement. To get a list of fixed properties, use the describeType() function, which is in the flash.utils package.

var myObject:Object = {firstName:"Tara", age:27, city:"San Francisco"}; 
for (var prop in myObject) { 
	trace("myObject."+prop+" = "+myObject[prop]); 
} 
/*
myObject.firstName = Tara 
myObject.age = 27 
myObject.city = San Francisco
*/

var myObject:Object = {firstName:"Tara", age:27, city:"San Francisco"}; 
for (var name in myObject) { 
	if (typeof (myObject[name]) == "string") { 
		trace("I have a string property named "+name); 
	} 
}
/*
I have a string property named city
I have a string property named firstName
*/

More examples

Related API Elements

for each (variableIterant in object){ 
	// statement(s)
} 

Iterates over the items of a collection and executes statement for each item. Introduced as a part of the E4X language extensions, the for each..in statement can be used not only for XML objects, but also for objects and arrays. The for each..in statement iterates only through the dynamic properties of an object, not the fixed properties. A fixed property is a property that is defined as part of a class definition. To use the for each..in statement with an instance of a user-defined class, you must declare the class with the dynamic attribute.

Unlike the for..in statement, the for each..in statement iterates over the values of an object's properties, rather than the property names.

var myObject:Object = {firstName:"Tara", age:27, city:"San Francisco"}; 
for each (var item in myObject) { 
	trace(item); 
} 
/*
Tara
27
San Francisco
*/

var myArray:Array = new Array("one", "two", "three"); 
for each(var item in myArray) 
	trace(item); 
/*
one
two
three
*/

var myObject:Object = {firstName:"Tara", age:27, city:"San Francisco"}; 
for each (var item in myObject) { 
	if (item is String) {  
		trace("I have a string property with value " + item); 
	} 
}

/*
I have a string property with value Tara
I have a string property with value San Francisco
*/

var doc:XML = 
		
			
Hello
			
Hola
			

			
Bonjour
		;
for each (var item in doc.p) {
	trace(item);
}

/*
Hello
Hola
Bonjour
*/

More examples

function functionName([parameter0, parameter1,...parameterN]) : returnType{ 
	// statement(s) 
} 
var functionName:Function = function ([parameter0, parameter1,...parameterN]) : returnType{ 
	// statement(s) 
} 

Comprises a set of statements that you define to perform a certain task. You can define a function in one location and invoke, or call, it from different scripts in a SWF file. When you define a function, you can also specify parameters for the function. Parameters are placeholders for values on which the function operates. You can pass different parameters to a function each time you call it so you can reuse the function in different situations.

Use the return statement in a function's statement(s) block to cause a function to generate, or return, a value.

Usage 1: You can use the function keyword to define a function with the specified function name, parameters, and statements. When a script calls a function, the statements in the function's definition are executed. Forward referencing is permitted; within the same script, a function may be declared after it is called. A function definition replaces any prior definition of the same function. You can use this syntax wherever a statement is permitted.

Usage 2: You can also use function to create an anonymous function and return a reference to it. This syntax is used in expressions and is particularly useful for installing methods in objects.

For additional functionality, you can use the arguments object in your function definition. The arguments object is commonly used to create a function that accepts a variable number of parameters and to create a recursive anonymous function.

function sqr(xNum:Number) { 
	return Math.pow(xNum, 2); 
} 
var yNum:Number = sqr(3); 
trace(yNum); // 9

var yNum:Number = sqr(3); 
trace(yNum); // 9 
function sqr(xNum:Number) { 
	return Math.pow(xNum, 2); 
}

Related API Elements

function get property() : returnType{ 
	// your statements here 
}

Defines a getter, which is a method that can be read like a property. A getter is a special function that returns the value of a property declared with the var or const keyword. Unlike other methods, a getter is called without parentheses (()), which makes the getter appear to be a variable.

Getters allow you to apply the principle of information hiding by letting you create a public interface for a private property. The advantage of information hiding is that the public interface remains the same even if the underlying implementation of the private property changes.

Another advantage of getters is that they can be overridden in subclasses, whereas properties declared with var or const cannot.

A getter can be combined with a setter to create a read-write property. To create a read-only property, create a getter without a corresponding setter. To create a write-only property, create a setter without a corresponding getter.

package {
	public class Team { 
		var teamName:String; 
		var teamCode:String; 
		var teamPlayers:Array = new Array(); 
		public function Team(param_name:String, param_code:String) { 
			teamName = param_name; 
			teamCode = param_code; 
		} 
		public function get name():String { 
			return teamName; 
		} 
		public function set name(param_name:String):void { 
			teamName = param_name; 
		}
	} 
}

var giants:Team = new Team("San Fran", "SFO"); 
trace(giants.name); 
giants.name = "San Francisco"; 
trace(giants.name); 
/*
San Fran San Francisco */

Related API Elements

if (condition) {
	// statement(s)
}

Evaluates a condition to determine the next statement to execute. If the condition is true, Flash Player runs the statements that follow the condition inside curly braces ({}). If the condition is false, Flash Player skips the statements inside the curly braces and runs the statements following the curly braces. Use the if statement along with the else statement to create branching logic in your scripts.

The curly braces ({}) that enclose the statements to be executed by the if statement are not necessary if only one statement will execute.

Related API Elements

myClass implements interface01 [, interface02 , ...] 

Specifies that a class implements one or more interfaces. When a class implements an interface, the class must define all the methods declared in the interface. Any instance of a class that implements an interface is considered a member of the data type defined by the interface. As a result, the is operator returns true when the class instance is the first operand and the interface is the second; in addition, type coercions to and from the data type defined by the interface work.

Related API Elements

import packageName.className 
import packageName.*

Makes externally defined classes and packages available to your code. For example, if you want to use the flash.display.Sprite class in a script, you must import it. This requirement is different from previous versions of ActionScript, in which the import directive was optional.

After using the import directive, you can use the full class name, which includes the package name, or just the name of the class.

 
import flash.display.Sprite; 

// name of class only
var mySprite:Sprite = new Sprite();

// full class name
var mySprite:flash.display.Sprite = new flash.display.Sprite();

If there are several classes in the package that you want to access, you can import them all in a single statement, as shown in the following example:

import flash.display.*;

The import directive imports only the classes, functions, and variables that reside at the top level of the imported package. Nested packages must be explicitly imported.

If you import a class but do not use it in your script, the class is not exported as part of the SWF file. This means you can import large packages without being concerned about the size of the SWF file; the bytecode associated with a class is included in a SWF file only if that class is actually used. One disadvantage of importing classes that you do not need is that you increase the likelihood of name collisions.

// On Frame 1 of a FLA: 
import adobe.example.*; 
var myFoo:foo = new foo();

include "[path]filename.as"

Includes the contents of the specified file, as if the commands in the file are part of the calling script. The include directive is invoked at compile time. Therefore, if you make any changes to an included file, you must save the file and recompile any SWF files that use it.

 interface InterfaceName [extends InterfaceName ] {}

Defines an interface. Interfaces are data types that define a set of methods; the methods must be defined by any class that implements the interface.

An interface is similar to a class, with the following important differences:

• Interfaces contain only declarations of methods, not their implementation. That is, every class that implements an interface must provide an implementation for each method declared in the interface.
• Interface method definitions cannot have any attribute such as public or private, but implemented methods must be marked as public in the definition of the class that implements the interface.
• Multiple interfaces can be inherited by an interface by means of the extends statement, or by a class through the implements statement.

Unlike ActionScript 2.0, ActionScript 3.0 allows the use of getter and setter methods in interface definitions.

Related API Elements

[internal] var varName
[internal] const kName
[internal] function functionName()  { 
	// your statements here 
}
[internal] class className{
	// your statements here 
}
[internal] namespace nsName

Specifies that a class, variable, constant, or function is available to any caller within the same package. Classes, properties, and methods belong to the internal namespace by default.

Related API Elements

label: statement
label: {
    statements
}

Associates a statement with an identifier that can be referenced by break or continue. In nested loops, a break or continue statement that does not reference a label can skip only the rest of the immediate loop and does not skip the entire series of loops. However, if the statement that defines the entire series of loops has an associated label, a break or continue statement can skip the entire series of loops by referring to that label.

Labels also allow you to break out of a block statement. You cannot place a break statement that does not reference a label inside a block statement unless the block statement is part of a loop. If the block statement has an associated label, you can place a break statement that refers to that label inside the block statement.

outerLoop: for (var i:int = 0; i < 10; i++) {
	for (var j:int = 0; j < 10; j++) {
		if ( (i == 8) && (j == 0)) {
			break outerLoop;
		}
		trace(10 * i + j);
	}
}
/*
1
2
...
79
*/

foo: {
	trace("a");
	break foo;
	trace("b");
}
// a

Related API Elements

namespace name [= uri]

Allows you to control the visibility of definitions. Predefined namespaces include public, private, protected, and internal.

The following steps show how to create, apply, and reference a namespace:

• First, define the custom namespace using the namespace keyword. For example, the code namespace version1 creates a namespace called version1.
• Second, apply the namespace to a property or method by using your custom namespace in the property or method declaration. For example, the code version1 myProperty:String creates a property named myProperty that belongs to the version1 namespace
• Third, reference the namespace by using the use keyword or by prefixing an identifier with the namespace. For example, the code use namespace version1; references the version1 namespace for subsequent lines of code, and the code version1::myProperty references the version1 namespace for the myProperty property.

Related API Elements

native function functionName();
class className { 
	native function methodName();
}

Specifies that a function or method is implemented by Flash Player in native code. Flash Player uses the native keyword internally to declare functions and methods in the ActionScript application programming interface (API). This keyword cannot be used in your own code.  

null

A special value that can be assigned to variables or returned by a function if no data was provided. You can use null to represent values that are missing or that do not have a defined data type.

The value null should not be confused with the special value undefined. When null and undefined are compared with the equality (==) operator, they compare as equal. However, when null and undefined are compared with the strict equality (===) operator, they compare as not equal.

var testArray:Array = new Array();
testArray[0] = "fee";
testArray[1] = "fi";
testArray[4] = "foo";

for (i = 0; i < 6; i++) {
    if (testArray[i] == null) {
        trace("testArray[" + i + "] == null");
    }
}

/* 
testArray[2] == null
testArray[3] == null
testArray[5] == null
*/

Related API Elements

Defines methods of the ObjectProxy class. The ObjectProxy class methods are in their own namespace to avoid name conflicts in situations where a Proxy subclass contains instance method names that match any of the Proxy class method names.

override function name() { 
	// your statements here 
}

Specifies that a method replaces an inherited method. To override an inherited method, you must use the override attribute and ensure that the name, class property attribute, number and type of parameters, and the return type match exactly. It is an error to attempt to override a method without using the override attribute. Likewise, it is an error to use the override attribute if the method does not have a matching inherited method.

You cannot use the override attribute on any of the following:

• Variables
• Constants
• Static methods
• Methods that are not inherited
• Methods that implement an interface method
• Inherited methods that are marked as final in the superclass

Although you cannot override a property declared with var or const, you can achieve similar functionality by making the base class property a getter-setter and overriding the methods defined with get and set.

Related API Elements

package packageName {
    class someClassName { 
    } 
}

Allows you to organize your code into discrete groups that can be imported by other scripts. You must use the package keyword to indicate that a class is a member of a package.

Related API Elements

class className{ 
	private var varName;
	private const kName;
	private function methodName() { 
		// your statements here 
	}
	private namespace nsName;
}

Specifies that a variable, constant, or method is available only to the class that declares or defines it. Unlike in ActionScript 2.0, in ActionScript 3.0 private no longer provides access to subclasses. Moreover, private restricts access at both compile time and runtime. By default, a variable or function is available to any caller in the same package. Use this keyword if you want to restrict access to a variable or function.

You can use this keyword only in class definitions, not in interface definitions. You cannot apply private to a class or to any other package-level definitions.

class A { 
  private var alpha:String = "visible only inside class A"; 
  public var beta:String = "visible everywhere"; 
}
	
class B extends A {
  function B() {
    alpha = "Access attempt from subclass"; // error
  }
}

Related API Elements

class className{ 
	protected var varName;
	protected const kName;
	protected function methodName() { 
		// your statements here 
	}
	protected namespace nsName;
}

Specifies that a variable, constant, method, or namespace is available only to the class that defines it and to any subclasses of that class. The definition of protected in ActionScript 3.0 is similar to the definition of the ActionScript 2.0 version of private, except that protected restricts access at both compile time and runtime. By default, a variable or function is available to any caller within the same package. Use this keyword if you want to restrict access to a variable or function.

You can use this keyword only in class definitions, not in interface definitions. You cannot apply private to a class, or to any other package-level definitions.

The definition of protected in ActionScript 3.0 is more restrictive than that of protected in the Java programming language. In ActionScript 3.0 protected limits access strictly to subclasses, whereas in Java protected also allows access to any class in the same package. For example, if a class named Base contains a property marked as protected, in ActionScript 3.0 only classes that extend Base can access the protected property. In Java, any class in the same package as Base has access to the protected property even if the class is not a subclass of Base.

class A { 
  private var alpha:String = "visible only inside class A"; 
  protected var beta:String = "visible inside class A and its subclasses"; 
}
	
class B extends A {
  public function B() {
    beta = "Access attempt from subclass succeeded";
    trace(beta);  // Access attempt from subclass succeeded
  }
}

Related API Elements

public var varName
public const kName
public function functionName()  { 
	// your statements here 
}
public class className {
	// your statements here 
}
public namespace nsName

Specifies that a class, variable, constant, or method is available to any caller. Classes, variables, and methods are internal by default, which means that they are visible only within the current package. To make a class, variable, or method visible to all callers, you must use the public attribute.

class User { 
	public var age:Number; 
	public var fname:String; 
} // end of class User definition
 
var jimmy:User = new User(); 
jimmy.age = 27; 
jimmy.fname = "jimmy";
trace(jimmy.age, jimmy.fname); // 27 jimmy

Related API Elements

function functionName () {
	return [expression]
}

Causes execution to return immediately to the calling function. If the return statement is followed by an expression, the expression is evaluated and the result is returned.

If a function definition includes a return type, the return statement must be followed by an expression. If no return type is specified and the return statement is used alone, it returns undefined.

You cannot return multiple values. If you try to do so, only the last value is returned. In the following example, c is returned:

return a, b, c ;

If you need to return multiple values, use an array or object instead.

function sum(a:Number, b:Number, c:Number):Number { 
	return (a + b + c); 
} 
var newValue:Number = sum(4, 32, 78); 
trace(newValue); // 114

Related API Elements

function set property(newValue:*) : void{ 
	// your statements here 
}

Defines a setter, which is a method that appears in the public interface as a property. A setter is a special method that sets the value of a property declared with the var keyword. Unlike other methods, a setter is called without parentheses (()), which makes the setter appear to be a variable.

Setters allow you to apply the principle of information hiding by letting you create a public interface for a private property. The advantage of information hiding is that the public interface remains the same even if the underlying implementation of the private property changes.

Another advantage of setters is that they can be overridden in subclasses, whereas properties declared with var cannot.

The return type of a setter must be either void or not specified.

A setter can be combined with a getter to create a read-write property. To create a read-only property, create a getter without a corresponding setter. To create a write-only property, create a setter without a corresponding getter.

package {
	class User { 
	    private var userAge:Number; 
	    
	    public function get age():Number {
	    	return userAge;
	    }
	    
	    public function set age(x:Number):void {
	    	userAge = x;	
	    }
	} 
} 

var myUser:User = new User();
myUser.age = 25;
trace(myUser.age); // 25

Related API Elements

class someClassName{ 
	static var varName; 
	static const kName;
	static function methodName() { 
		// your statements here
	} 
}

Specifies that a variable, constant, or method belongs to the class, rather than to instances of the class.

To access a static class member, use the name of the class instead of the name of an instance. For example, the Date class has a static method named parse(), which can only be called using the following syntax:

Date.parse()

The parse() method cannot be called on an instance of the Date class. For example, the following code generates an error:

var myDate:Date = new Date();
            myDate.parse("Jan 01 00:00:00 2006"); // error

You can use static in class definitions only, not in interface definitions.

Static class members are not inherited. You cannot refer to a static class member using the name of a subclass, as you can in Java or C++. You can, however, refer to a static variable or method within a class or subclass, without using any qualifier. See the example below.

You cannot use the super statement or the this keyword inside a static method.

class Users { 
	private static var numInstances:Number = 0; 
	function Users() { 
		numInstances++; 
	} 
	static function get instances():Number { 
		return numInstances; 
	} 
}

trace(Users.instances); 
var user1:Users = new Users(); 
trace(Users.instances); 
var user2:Users = new Users(); 
trace(Users.instances); 

class PowerUsers extends Users{
    function PowerUsers() {
        instances++;  // unqualified reference to static property Users.instances is legal
    }
}

trace(PowerUsers.instances); // error, cannot access static property using PowerUsers class

super([arg1, ..., argN])
super.method([arg1, ..., argN])

Invokes the superclass or parent version of a method or constructor. When used within the body of a class constructor, the super() statement invokes the superclass version of the constructor. The call to the superclass constructor must have the correct number of arguments. Note that the superclass constructor is always called, whether or not you call it explicitly. If you do not explicitly call it, a call with no arguments is automatically inserted before the first statement in the subclass constructor body. This means that if you define a constructor function in a subclass, and the superclass constructor takes one or more arguments, you must explicitly call the superclass constructor with the correct number of arguments or an error will occur. The call to the superclass constructor, however, does not need to be the first statement in your subclass constructor, as was required in ActionScript 2.0.

When used in the body of an instance method, super can be used with the dot (.) operator to invoke the superclass version of a method and can optionally pass arguments (arg1 ... argN) to the superclass method. This is useful for creating subclass methods that not only add additional behavior to superclass methods, but also invoke the superclass methods to perform their original behavior.

You cannot use the super statement in a static method.

Related API Elements

switch (expression) {
	caseClause: 
	[defaultClause:] 
}

Causes control to transfer to one of several statements, depending on the value of an expression. All switch statements should include a default case that will execute if none of the case statements match the expression. Each case statement should end with a break statement, which prevents a fall-through error. When a case falls through, it executes the code in the next case statement, even though that case may not match the test expression.

var switchExpression:int = 3;
		
switch (switchExpression) {
	case 0:
		trace(0);
		break;
	case 1:
		trace(1);
		break;
	case 2:
		trace(2);
		break;
	default:
		trace("Not 0, 1, or 2");
}

// Not 0, 1, or 2

Related API Elements

this

A reference to a method's containing object. When a script executes, the this keyword references the object that contains the script. Inside a method body, the this keyword references the class instance that contains the called method.

// incorrect version of Simple.as
/*
dynamic class Simple {
    function callfunc() {
        func();
    }
}
*/
// correct version of Simple.as
dynamic class Simple {
    function callfunc() {
        this.func();
    }
}

var simpleObj:Simple = new Simple();
simpleObj.func = function() {
	trace("hello there");
}
simpleObj.callfunc();

throw expression 

Generates, or throws, an error that can be handled, or caught, by a catch code block. If an exception is not caught by a catch block, the string representation of the thrown value is sent to the Output panel. If an exception is not caught by a catch or finally block, the string representation of the thrown value is sent to the log file.

Typically, you throw instances of the Error class or its subclasses (see the Example section).

function checkEmail(email:String) { 
	if (email.indexOf("@") == -1) { 
		throw new Error("Invalid email address"); 
	} 
} 
checkEmail("someuser_theirdomain.com");

try { 
	checkEmail("Joe Smith"); 
} 
catch (e) { 
	trace(e); 
}
// Error: Invalid email address.

// Define Error subclass InvalidEmailError 
class InvalidEmailAddress extends Error { 
    public function InvalidEmailAddress() {
    	message = "Invalid email address."; 
    }
}

import InvalidEmailAddress; 
function checkEmail(email:String) { 
	if (email.indexOf("@") == -1) { 
		throw new InvalidEmailAddress(); 
	} 
} 
try { 
	checkEmail("Joe Smith"); 
} 
catch (e) { 
	trace(e);
}
// Error: Invalid email address.

More examples

Related API Elements

true

A Boolean value representing true. A Boolean value is either true or false; the opposite of true is false. When automatic data typing converts true to a number, it becomes 1; when it converts true to a string, it becomes "true".

var shouldExecute:Boolean;
// ...
// code that sets shouldExecute to either true or false goes here
// shouldExecute is set to true for this example:

shouldExecute = true;

if (shouldExecute == true) {
    trace("your statements here");
}

// true is also implied, so the if statement could also be written:
// if (shouldExecute) {
//         trace("your statements here");
// }

var myNum:Number;
myNum = 1 + true;
trace(myNum); // 2

Related API Elements

try { 
    // try block 
} finally { 
    // finally block  
} 

try { 
    // try block 
} catch(error[:ErrorType1]) {
    // catch block 
} [catch(error[:ErrorTypeN]) { 
    // catch block 
}] [finally {
    // finally block 
}]

Encloses a block of code in which an error can occur, and then responds to the error. Exception handling, which is implemented using the try..catch..finally statements, is the primary mechanism for handling runtime error conditions in ActionScript 3.0. When a runtime error occurs, Flash Player throws an exception, which means that Flash Player suspends normal execution and creates a special object of type Error. Flash Player then passes, or throws, the error object to the first available catch block. If no catch blocks are available, the exception is considered to be an uncaught exception. Uncaught exceptions cause the script to terminate.

You can use the throw statement to explicitly throw exceptions in your code. You can throw any value, but the best practice is to throw an object because it provides flexibility and matches the behavior of Flash Player.

To catch an exception, whether it is thrown by Flash Player or by your own code, place the code that may throw the exception in a try block. If any code in the try block throws an exception, control passes to the catch block, if one exists, and then to the finally block, if one exists. The finally block always executes, regardless of whether an exception was thrown. If code within the try block does not throw an exception (that is, if the try block completes normally), the code in the catch block is ignored, but the code in the finally block is still executed. The finally block executes even if the try block exits using a return statement.

A try block must be followed by a catch block, a finally block, or both. A single try block can have multiple catch blocks but only one finally block. You can nest try blocks as many levels deep as desired.

The error parameter specified in a catch handler must be a simple identifier such as e or theException or x. The parameter can also be typed. When used with multiple catch blocks, typed parameters let you catch multiple types of error objects thrown from a single try block.

If the exception thrown is an object, the type will match if the thrown object is a subclass of the specified type. If an error of a specific type is thrown, the catch block that handles the corresponding error is executed. If an exception that is not of the specified type is thrown, the catch block does not execute and the exception is automatically thrown out of the try block to a catch handler that matches it.

If an error is thrown within a function, and the function does not include a catch handler, Flash Player exits that function, as well as any caller functions, until a catch block is found. During this process, finally handlers are called at all levels.

Note: If in a try block, there is an event dispatcher that calls its event handler, the catch block doesn't catch the error if thrown in event handler. Any error thrown thereafter can be caught by listening to LoaderInfo.uncaughtErrorEvents.

import flash.display.Sprite;

var spr:Sprite = new Sprite();
try {
	spr.addChild(spr);
}
catch (e:ArgumentError) {
	trace (e); // ArgumentError: Error #2024: An object may not be added as a child of itself.
}

class RecordSetException extends Error { 
	public function RecordSetException () {
		message = "Record set exception occurred."; 
	}
}

class MalformedRecord extends Error { 
	public function MalformedRecord {
		message = "Malformed record exception occurred."; 
	}
}

class RecordSet { 
	public function sortRows() { 
		var returnVal:Number = randomNum(); 
		if (returnVal == 1) { 
			throw new RecordSetException(); 
		} 
		else if (returnVal == 2) { 
			throw new MalformedRecord(); 
		} 
	}
	public function randomNum():Number { 
		return Math.round(Math.random() * 10) % 3; 
	}
}

import RecordSet; 
var myRecordSet:RecordSet = new RecordSet();
try { 
	myRecordSet.sortRows(); 
	trace("everything is fine"); 
} 
catch (e:RecordSetException) { 
	trace(e.toString()); 
} 
catch (e:MalformedRecord) { 
	trace(e.toString()); 
}

More examples

Related API Elements

use namespace ns1[, ns2, ...nsN]

Causes the specified namespaces to be added to the set of open namespaces. The specified namespaces are removed from the set of open namespaces when the current code block is exited. The use namespace directive can appear at the top level of a program, package definition, or class definition.

Related API Elements

var variableName [= value1][...,variableNameN[=valueN]] 

Specifies a variable. If you declare variables inside a function, the variables are local. They are defined for the function and expire at the end of the function call.

You cannot declare a variable that is in the scope of another object as a local variable.

my_array.length = 25; // ok 
var my_array.length = 25; // syntax error 

You can assign a data type to a variable by appending a colon character followed by the data type.

You can declare multiple variables in one statement, separating the declarations with commas (although this syntax may reduce clarity in your code):

var first:String = "Bart", middle:String = "J.", last:String = "Bartleby";

var product_array:Array = new Array("Studio", "Dreamweaver", "Flash", "ColdFusion", "Contribute", "Breeze"); 
product_array.push("Flex"); 
trace(product_array); 
// Studio,Dreamweaver,Flash,ColdFusion,Contribute,Breeze,Flex

Related API Elements

while (condition) { 
	// statement(s)
}

Evaluates a condition and if the condition evaluates to true, executes one or more statements before looping back to evaluate the condition again. After the condition evaluates to false, the statements are skipped and the loop ends.

The while statement performs the following series of steps. Each repetition of steps 1 through 4 is called an iteration of the loop. The condition is tested at the beginning of each iteration, as shown in the following steps:

1. The expression condition is evaluated.
2. If condition evaluates to true or a value that converts to the Boolean value true, such as a nonzero number, go to step 3. Otherwise, the while statement is completed and execution resumes at the next statement after the while loop.
3. Run the statement block statement(s). If a continue statement is encountered, skip the remaining statements and go to step 1. If a break statement is encountered, the while statement is completed and execution resumes at the next statement after the while loop.
4. Go to step 1.

Looping is commonly used to perform an action while a counter variable is less than a specified value. At the end of each loop, the counter is incremented until the specified value is reached. At that point, the condition is no longer true, and the loop ends.

The curly braces ({}) that enclose the statements to be executed by the while statement are not necessary if only one statement will execute.

var i:Number = 0; 
while (i < 20) { 
	trace(i); 
	i += 3; 
}
/*
0 
3 
6 
9 
12
15 
18
*/

Related API Elements

with (object:Object) { 
	// statement(s)
}

Establishes a default object to be used for the execution of a statement or statements, potentially reducing the amount of code that needs to be written.

The object parameter becomes the context in which the properties, variables, and functions in the statement(s) parameter are read. For example, if object is my_array, and two of the properties specified are length and concat, those properties are automatically read as my_array.length and my_array.concat. In another example, if object is state.california, any actions or statements inside the with statement are called from inside the california instance.

To find the value of an identifier in the statement(s) parameter, ActionScript starts at the beginning of the scope chain specified by object and searches for the identifier at each level of the scope chain, in a specific order.

The scope chain used by the with statement to resolve identifiers starts with the first item in the following list and continues to the last item:

• The object specified in the object parameter in the innermost with statement
• The object specified in the object parameter in the outermost with statement
• The Activation object (a temporary object that is automatically created when the script calls a function that holds the local variables called in the function)
• The object that contains the currently executing script
• The Global object (built-in objects such as Math and String)

To set a variable inside a with statement, you must have declared the variable outside the with statement, or you must enter the full path to the Timeline on which you want the variable to live. If you set a variable in a with statement without declaring it, the with statement will look for the value according to the scope chain. If the variable doesn't already exist, the new value will be set on the Timeline from which the with statement was called.

function polar(r:Number):void { 
	var a:Number, x:Number, y:Number; 
	with (Math) { 
		a = PI * pow(r, 2); 
		x = r * cos(PI); 
		y = r * sin(PI / 2); 
	} 
	trace("area = " + a); 
	trace("x = " + x); 
	trace("y = " + y); 
} polar(3);
/* 
area = 28.2743338823081 
x = -3 
y = 3
*/