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Flash Actionscript Programming Basics
Author: Steve Happ | Website: http://www.video-animation.com |

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Functions

A function is a named unit, in which statements are logically grouped. It usually contains the following parts:

• Function Name - e.g. function someName( )
• Argument list - is enclosed within parentheses after the function name. It contains a comma-separated list of 0 or more arguments. Arguments are passed to the variable with the same name as the argument inside the function.
• Return Type - the datatype of what the function can evaluate to.
• The function Body - is enclosed within a pair of braces { } and contains a sequence of statements.

Here is a template. For AS 1.0 :

Function functionName(arg1, arg2, arg3){
 // statements go here
 return something if not void return type;
 }

example1 (AS 1.0). Type this and compile (Control+Enter):

function test1(arg1, arg2){
// arg1 is passed to the variable with the same name
// in the next line I.e. arg1
 trace(arg1);
 trace(arg2);
}
// call function
test1(3,"Steve");

Notice that to call a function we write the function name and the argument lists in parentheses. Template to call a function:

 functionName(arg1, arg2);

Example 2 with a return value (AS 1.0)

function returnTest(arg1){
 var num = arg1 * 10;
 return num;
}
// call function
trace(returnTest(5));

ex. 3

// returns the absolute value of number
 function abs(number){
return( i <0 ? -i : i);
}
// call the method
trace(abs(-350.95);
ex 4
// return the smaller of two values.
function min(num1,num2){
return(num1 <= num2 ? num1: num2);
}
trace(min(27,45));

Functions in AS 2.0

Functions in AS 2.0 are a little different. AS 2.0 allows the setting of specific datatypes. Here is an example :

Function avgReturn(arg1:Number):Number{
Var num = arg1 * 5;
return num;
}

The template for an AS 2.0 function could be :

Function functionName(arg1:DataType,
 arg2:DataType):ReturnType{
// statements go here
return something ;
}

Void is used to specify that there is no return type. E.g.

function noReturn(arg1:Number,
 arg2:String):Void{
trace(arg2+" is a string and "+arg1+" is a number");
}
// call function
noReturn(5,"Steve");

Arrays

An array is a collection of objects . Individual objects are not named but accessed by its position in the array. Try this!

var theArray = new Array(5,4,8,2,1);
for(var i = 0;i<5;i++){
 trace(theArray[i]);
}

Elements are numbered beginning with "0".
In the above array
theArray[0] = 5
theArray[2] = 8
Length is a property of Array. It tells how many elements are in the array. So , from above,
theArray.length = 5

Classes

(As 2.0 only)
A class is a user-defined datatype, an aggregate of named data elements, and a set of operations to manipulate that data. A class definition consists of two parts:

1. The class head - composed of the keyword class and a name
2. the class body - enclosed by braces, contains the member definitions

A class name represents a new data type . e.g.

class Dog{
 // data members
 var name:String;
 var age:Number;
 // class method
 function setAge(age1:Number){
 age = age1;
 }
}

Constructors allow us to create an instance of a class . e.g.

var rusty:Dog = new Dog();
// the dot operator (".")
// allows us to access members and methods of that class.
rusty.setAge(7);
rusty.name = "Rusty";

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Added: : 2005-08-10 Rating: 8.17 Votes: 12 Hits: 674

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Steve Happ is the founder of Steve's Tutes and has been going hard at it developing Flash for Web and CD-rom.

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