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Flash Reference Guide

Aug 22, 2003

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In past guides I have covered the use of Strings, data comprised of numbers and letters. In this section of the guide I am going to discuss Numbers. The Number data type is the foundation for the Math class. You will find that as you develop more and more complex solutions, you will need to leverage the power of the Number data type to perform mathematical equations. You will need this skill whether you are developing an online shopping cart, a graphing tool, any type of game, or other solutions.

You will discover that the Number data type is a double-precision floating-point number. The minimum value of a number object is approximately 5e-324. The maximum is approximately 1.79E+308. Do you have an idea of how big these numbers are? Well, let's just say they are really big.

As I mentioned before, you can leverage the Number data type with arithmetic operators addition (+), subtraction (-), multiplication (*), division (/), modulo (%), increment (++), and decrement (--). The following is then true:

var myCount:Number = 0;
myCount = 10 + 5;
trace("There are " + myCount + " items on the shelf.");

The answer you will receive is "There are 15 items on the shelf." Using arithmetic operators, you can play around and generate different answers. For instance, the following script is similar, with the addition of just one new line of code.

var myCount:Number = 0;
myCount = 10 + 5;
myCount--;
trace("There are " + myCount + " items on the shelf.");

Now The answer is "There are 14 items on the shelf."

The decrement operator (--) reduces the value by 1. The increment operator (++) will increase the value by 1, as demonstrated below:

var myCount:Number = 0;
myCount = 10 + 5;
myCount++;
trace("There are " + myCount + " items on the shelf.");

Now the result is "There are 16 items on the shelf."

Multiplication and division operators can also be used with the Number operator. The following examples demonstrate the multiplication operator (*) and division operator (/).

var myCount:Number = 0;
myCount = 10 * 5;
trace("There are " + myCount + " items on the shelf.");

Now the answer is "There are 50 items on the shelf."

Using the division operator you receive the following response:

var myCount:Number = 0;
myCount = 10 / 5;
trace("There are " + myCount + " items on the shelf.");

Now the answer is "There are 2 items on the shelf."

Finally, the modulo operator calculates the remainder of expression1 divided by expression2. If either of the expression parameters are non-numeric, the modulo (%) operator attempts to convert them to numbers. The expression can be a number or string that converts to a numeric value. The following example demonstrates this:

var myCount:Number = 0;
myCount = 10 % 5;
trace("There are " + myCount + " items on the shelf.");

Now the answer is "There are 0 items on the shelf."

Now, let’s write a simple class that allows you to exercise the use of the Number operator. The following class is one you can use if you need drag and drop functionality in your Flash movies:

/*------------------------------------------------------------------------------------------------------------
|
| Instantiate new instance of DragnDrop class as follows:
| var varname:DragnDrop = new DragnDrop(dragObj, targetObj, _enabled, _alpha, _visible, _play, _mainPlay);
|                                                      |
| Arguments for constructor are as follows:
| 1.) dragObj:Object = Object to drag
| 2.) targetObj:Object = Target Object
| 3.) _enabled:Boolean = Disable Drag Object
| 4.) alpha:Number = Change _alpha of Drap Object
| 5.) _visible:Boolean = Visibility of Drag Object
| 6.) _play:Number = Drag Object - play frame number
| 7.) _mainPlay:Number = Main timeline / _level - play frame number                     |
|
| Sample:
| var dd:DragnDrop = new DragnDrop(this.circle, this.square, null, 80, true, null, null);
|                                                      |
-------------------------------------------------------------------------------------------------------------*/



class DragnDrop

{
    
    private var drag:Object;
    private var target:Object;
    private static var _this:Object;
    
    private var drag_x:Number;
    private var drag_y:Number;
    private var target_x:Number;
    private var target_y:Number;
    private var enabled:Boolean;
    private var alpha:Number;
    private var visible:Boolean;
    private var dragPlay:Number;
    private var mainPlay:Number;
    
    
    
    // constructor for DragnDrop class - dragObj, targetObj, _enabled, _alpha, _visible, _play, _mainPlay
    function DragnDrop(dragObj:Object, targetObj:Object, _enabled:Boolean, alpha:Number, _visible:Boolean, _play:Number, _mainPlay:Number) {
        DragnDrop._this = this;
        this.drag = dragObj;
        this.target = targetObj;
        this.drag_x = dragObj._x;
        this.drag_y = dragObj._y;
        this.target_x = targetObj._x;
        this.target_y = targetObj._y;
        this.enabled = _enabled;
        this.alpha = alpha;
        this.visible - _visible;
        this.dragPlay = _play;
        this.mainPlay = _mainPlay;
        build();
    }
    
    
    private function build():Void {
        this.drag.onPress = function() {
            DragnDrop._this.Drag();
        };
        this.drag.onRelease = function() {
            DragnDrop._this.Drop();
        };
    }
    
    
    private function Drag():Void {
        this.drag.startDrag();
    }
    
    
    private function Drop():Void {
        this.drag.stopDrag();
        if (eval(this.drag._droptarget) == this.target) {
            this.drag.enabled = this.enabled;
            this.drag._alpha = this.alpha;
            this.drag.gotoAndPlay(this.dragPlay);
            this.drag._visible = this.visible;
            this.drag._x = this.target_x;
            this.drag._y = this.target_y;
            gotoAndStop(mainPlay);
        } else {
            this.drag._x = this.drag_x;
            this.drag._y = this.drag_y;
        }
    }
    
}

As you can see, the Number operator allows you to control mathematically events in your scripts. The next section of the guide will look deeper into the abilities of the Number class.

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