Variables in Actionscript

Previously:

Dot Notation
Properties and Functions
addEventListener();
Creating MouseEvents
Interactive Storybook Example FLA

Today:

Actionscript Vars
Interactive Storybook Assignment

http://goo.gl/mEJQdT

Variables in Actionscript

What is a Variable or Var?

Variables in Actionscript

Variables are Containers of Value

We've all seen and used variables before!

Algebra:

5 + X = 7
9 - B = 3

Variables in Actionscript

Variables are Containers of Value

Variables can contain different types of values

                               4 + t = 18

                             "happy" + t + "year" = "happy new year"

                                                                          t = true

Variables in Actionscript

Some of the different Variable types:

Number
String
Int
MovieClip
Button
Event
Boolean

Variables in Actionscript

In Actionscript there are words that the computer understands:

gotoAndPlay()
stop()
function
var
addEventListener()
alpha
void

Variables in Actionscript

Declaring a new Variable or Var is like giving
your computer new vocabulary words

                                                 var highScore : Number;
                                                 var screenMessage : String;
                                                 var playerAlive : Boolean;
                                                 var healthPoints : Int;

            You define a variable with a name and a type

Variables in Actionscript

Declaring a function is also defining new vocabulary words

                                                 function bark():void{
                                                          gotoAndPlay("bark");
                                                  }

            You define a function with a name , input, output,
             list of instructions

Variables in Actionscript

The Core of All Programming

Manipulating Variables (containers of value)
and Displaying the Results on screen

Manipulating Variables in Actionscript

Change the values inside Variables - (Operators)
Comparing the values inside Variables - (Conditionals)

Manipulating Variables in Actionscript

Create Example Using MOUSE Events:

Use Variables for position and velocity

Introduction to the ENTER_FRAME event

The ENTER_FRAME event occurs during the time
between screen refresh rates.

The framerate of a FLA determines how often the
screen refreshes or redraws itself.

Introduction to the ENTER_FRAME

Modifying variables inside the ENTER_FRAME and
updating MC position between the screen refresh.

It is how you animate screen objects using code.

Animating Using Variables in Actionscript

Create Example Using ENTER_FRAME Event:

Use Variables for position and velocity

and Introduce new Variable type - Boolean (true or false)

Animating Using Variables in Actionscript

Example: Using both ENTER_FRAME and MOUSE Event:

Use Variables for position, velocity and gravity

and Use another Variable type - String ("text")

Intro to Game Engine Loop

The basis of almost all arcade style video games.

This loop happens on every screen refresh/update.

Contains at least these three parts:

Manipulating Game Variables
Updating On-Screen Game Objects
Collision Detection

Intro to Game Engine Loop

Typical Game Loop Inside Actionscript:

function gameLoop():void{

updateGame();

updateScreenDisplay();

checkCollisions();

}

and gameLoop gets called on every ENTER_FRAME.

Intro to Game Engine Loop

Simple Collision Detection Inside Actionscript.

hitTestObject()

We can determine if two on-screen MovieClips overlap.

if ( MovieClip1, hitTestObject(MovieClip2) ) {

// ** Collision Detected **

}