Flash / Flex / ActionScript/Data Type/Variable Declare

It is a good practice to initialize your variables to null when you don"t have any other specific value to assign to them

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var myVariable:Number = null;
       trace(myVariable);
       
       var sMessage:String = "Welcome!";
       trace(sMessage);
   }
 }

}

       </source>
   
  

Once a variable has been declared, you can assign a value to it using a simple assignment statement with an equals sign

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var myVariable:Number;
       myVariable = 6;
       trace(myVariable);
   }
 }

}

       </source>
   
  

Overriding Variables

   <source lang="java">

objects defined in more localized scopes will always override objects defined in more global scopes. package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var myLocal:Local = new Local();
       trace(myLocal.a); // Displays: instance
       trace(myLocal.b); // Displays: instance
       
       myLocal.method(); // Displays: function
       
   }
 }

} class Local {

     public var a:String = "instance";
     public var b:String = "instance";
     public function method():void {
        var a:String = "function";
        b = "function";
        trace(a);
        trace(b);
     }

}

       </source>
   
  

Perform operations using variables

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var myVariable:Number = 6;
       var nPrice:Number = 9.99;
       trace(myVariable * nPrice);  // Displays: 59.94
   }
 }

}

       </source>
   
  

To declare a variable using strong typing: var variableName:Datatype;

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var myVariable:Number;
       trace(myVariable);
   }
 }

}

       </source>
   
  

To declare the data type of a variable, use the colon operator right after the name of the variable.

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var x:Number;
       var name:String = "Mims";
       
       x = 42;    // No problem
       x = -13;   // No problem
       x = 3.141; // No problem
   }
 }

}

       </source>
   
  

Use the this keyword when referring to an instance variable with the same name as a function variable:

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   var foo;
  
   public function Main(){

   }public function setFoo (foo:String):void {
       this.foo = foo;

}

 }

}

       </source>
   
  

Using Access Controls

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   private var lunchtime:Date;
   public function Main(){
   }
 }

}

       </source>
   
  

Using Untyped Variables with the Wildcard (*) Data Type

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var x:*;
       
       x = 3;
       trace(x);
       x = "name";
       trace(x);
   }
 }

}

       </source>
   
  

You can also declare the variable and assign a value, or initialize the variable, all on one line

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var myVariable:Number = 6;
       trace(myVariable);
   }
 }

}

       </source>
   
  

You can declare several variables on a single line

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var breakfast:String, lunch:String, dinner:String;

   }
 }

}

       </source>