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Writing custom functions

From: ActionScript 3.0 in Flash CS3 Professional Essential Training

Video: Writing custom functions

In this movie we'll write a custom function that will make our snowboarder jump up into the air and turn a little bit. If you'd like to follow along, this in the chapter 3 Exercise Folder and the file is called WritingFunctions.fla. This is a very simple file. It has a movie clip called mcBoarder. You can verify in the library that's the name of the movie clip, and it's just a png image. And I just drew some snow so he can have some turf to ride on. Okay, let's write the code that will make this movie clip move.

Writing custom functions

In this movie we'll write a custom function that will make our snowboarder jump up into the air and turn a little bit. If you'd like to follow along, this in the chapter 3 Exercise Folder and the file is called WritingFunctions.fla. This is a very simple file. It has a movie clip called mcBoarder. You can verify in the library that's the name of the movie clip, and it's just a png image. And I just drew some snow so he can have some turf to ride on. Okay, let's write the code that will make this movie clip move.

So first I'm going to click on this boarder and just make sure that he has an instance name, and there is an instance name and it is boarder_mc. So if we want to communicate with ActionScript to the snowboarder we're going to refer to him as boarder_mc. I'm going to go up to the actions layer, click the first keyframe of that layer. I'm going to make sure it's locked. Select that keyframe, press Option+F9 or F9 on the PC to open on the actions panel. Now what we're going to do is the same thing we did before when we changed properties of an object except we're going to put it inside of a function.

In the next movie we'll explore how to make this function more useful. But for right now, let's just type the word function, and then a space. And I'm going to call this function moveBoarder. Defining a function is similar to defining a variable. Instead of typing var and a space and the variable name, you type function and a space and the function name. So we're going to build our reusable block of code here. So function moveBoarder().

And we need to put parentheses, always when we create function and in the next movie I'll explain what you put inside the parentheses. And then I'm going to type a colon and and that's going to specify the return datatype. I haven't yet explained the return datatype and we'll cover that in a later movie. But I'm going to type void for now, with a lowercase V, that means there is no return datatype. Press Enter or Return to go to the next line. Open curly brace, next line, close curly brace. up arrow, and then Enter or Return.

And inside of these curly braces is where we write what happens in the moveBoarder function. So all I'm going to do is adjust the boarder's position. So I'm going to type boarder_mc, that's our boarder instance name, dot y, and type space equal space, and then type 50; We're going to set the y-positioning of boarder_mc to 50. That's going to be 50 pixels from the top of our Flash movie and not from the bottom.

Remember Flash counts pixels from the top left, not the bottom left like in math class. Now let's rotate our boarders. So I'm going to press Enter or Return to go to the next line. And I'm going to type boarder_mc .rotation space equal space 45, let's type a ; And now if we were to test the movie right now, nothing would happen. Just like I explained at the beginning of this chapter how we had to drag elements inside of the function box and that didn't necessarily run the function. We had to click the run function button. That's what we're doing here. We're putting things inside of the function block of code.

We have not ran the function yet. So we need to do something else to run the function. And that something else is like we did in last movie when we ran go to and stop and we ran the stop function. So I'm going to click right after this curly brace on line 5 and I'm going to press Enter or Return twice to go down 2 lines. You don't have to go down 2 lines, you can go down just one line, I just like to space out my code. And then if we want to run this function, we need to type and moveBoarder, which is the name of our function, (); Notice how that looks exactly like stop.

Stop(); That actually runs the function. So I'm going to close this Actions window. Just take a note of where the boarder is currently. Test the movie and notice that it jumps to the top of the screen. So if you move over the movie, you can notice that he's also rotated. Now that you know how to write a custom function, let's learn how to make our functions more useful.

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This video is part of

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  1. 2m 3s
    1. Introduction
      39s
    2. How to use the exercise files
      1m 24s
  2. 3m 53s
    1. Why you should learn ActionScript 3.0
      52s
    2. Differences from ActionScript 2.0
      1m 56s
    3. Moving beyond Script Assist
      1m 5s
  3. 21m 57s
    1. Communicating to MovieClips
      4m 7s
    2. Modifying MovieClips properties
      7m 0s
    3. Understanding variables
      50s
    4. Setting variable data types
      3m 23s
    5. Using trace statements
      2m 39s
    6. Using comments
      3m 58s
  4. 26m 3s
    1. Understanding functions
      1m 23s
    2. Using functions
      2m 27s
    3. Writing custom functions
      4m 25s
    4. Making a function modular
      11m 50s
    5. Making a function return a value
      5m 58s
  5. 41m 45s
    1. Understanding event types
      1m 28s
    2. Using a listener to catch an event
      3m 14s
    3. Writing event handlers
      6m 56s
    4. Responding to mouse events
      4m 33s
    5. Responding to keyboard events
      5m 45s
    6. Creating a link to a website
      5m 26s
    7. Using the enterframe to create animation
      7m 34s
    8. Using the timer event to control animation
      6m 49s
  6. 44m 32s
    1. Understanding classes
      1m 48s
    2. Writing a custom class
      4m 21s
    3. Extending an existing class
      2m 16s
    4. Understanding methods
      2m 11s
    5. Public vs. private properties and methods
      2m 46s
    6. Bringing a class object to the timeline
      14m 16s
    7. Defining a document class
      8m 13s
    8. Setting up a classpath
      6m 20s
    9. Creating useful classes
      2m 21s
  7. 36m 4s
    1. Understanding conditional statements
      1m 36s
    2. Writing a conditional statement
      4m 40s
    3. Understanding conditional operators
      1m 37s
    4. Using conditional operators
      4m 49s
    5. Setting up alternate conditions
      4m 43s
    6. Writing compound conditions
      4m 22s
    7. Understanding loops
      1m 30s
    8. Creating a code loop
      2m 58s
    9. Using a loop to generate instances of a class
      3m 44s
    10. Placing loop-created instances
      6m 5s
  8. 12m 49s
    1. Understanding the math class
      1m 5s
    2. Using basic math operators
      1m 46s
    3. Generating random numbers
      2m 15s
    4. Using different techniques to round numbers
      7m 43s
  9. 56m 20s
    1. Creating a text field
      3m 27s
    2. Styling a text field
      6m 28s
    3. Capturing data from a text field
      7m 38s
    4. Loading external text
      8m 25s
    5. Scrolling a text field
      5m 14s
    6. Understanding arrays
      9m 48s
    7. Using text and arrays to create a game
      8m 24s
    8. Finishing the text game
      6m 56s
  10. 1h 9m
    1. Storyboarding your application effectively
      3m 13s
    2. Writing a memory card class
      5m 57s
    3. Writing a memory game class
      3m 51s
    4. Adding graphics to cards
      9m 20s
    5. Placing cards
      7m 33s
    6. Detecting matches
      8m 40s
    7. Resetting cards
      4m 53s
    8. Handling incorrect matches
      5m 14s
    9. Determining a win
      3m 51s
    10. Adding additional cards
      6m 47s
    11. Randomizing cards
      10m 17s
  11. 36m 30s
    1. Drawing with code
      8m 12s
    2. Creating a color change
      5m 20s
    3. Generating a random color change
      6m 58s
    4. Animating a color change
      4m 50s
    5. Using filters
      3m 30s
    6. Modifying filter properties
      4m 13s
    7. Animating filters
      3m 27s
  12. 51m 50s
    1. Loading external images and Flash movies
      4m 1s
    2. Communicating to loaded movies
      6m 31s
    3. Loading sound
      4m 6s
    4. Starting and stopping sound
      6m 18s
    5. Pausing and resuming sound
      9m 46s
    6. Managing the volume of sound
      5m 41s
    7. Understanding Flash video connections
      1m 0s
    8. Loading video
      5m 33s
    9. Controlling video playback
      8m 54s
  13. 45m 54s
    1. Overview of creating a drag-and-drop game
      57s
    2. Creating drag-and-drop class
      12m 7s
    3. Detecting collisions
      8m 44s
    4. Responding to collisions
      9m 1s
    5. Detecting a win
      4m 2s
    6. Adding drop shadows
      3m 43s
    7. Randomly placing objects
      7m 20s
  14. 23s
    1. Closing
      23s

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