Chapter 1. A Gentle Introduction for Non-Programmers

1.1.1. Creating Code

1. Launch Flash with a new blank document.

2. On the main timeline, select frame 1 of layer 1.

3. Select Window Actions.

Figure 1-1. Flash 5 Basic Actions

Figure 1-2. Expanded Actions

The Toolbox pane's menus may be used to create ActionScript code. However, in order to learn the syntax, principles, and structural makeup of ActionScript, we'll be typing all our code.

TIP

So-called Actions are more than just Actions -- they include various fundamental programming-language tools: variables, conditionals, loops, comments, function calls, and so forth. Although these are lumped together in one menu, the generic name Action obscures the programming structures' significance.

We'll be breaking Actions down to give you a programmer's perspective on those structures. Throughout the book, I use the appropriate programming term to describe the Action at hand. For example, instead of writing, "Add a while Action," I'll write, "Create a while loop." Instead of writing, "Add an if Action," I'll write, "Make a new conditional." Instead of writing, "Add a play Action," I'll write, "Invoke the play( ) function (or method)." These distinctions are an important part of learning to speak ActionScript.

Ready to get your hands dirty? Let's say hello to Flash.

1.1.2. Say Hi to Flash

And now, the exciting moment -- your first line of code. It's time to introduce yourself to Flash! Type the following into the Script pane:

var message = "Hi there, Flash!";

var firstName = "your name here";
trace (message);

Hmmm. Nothing has happened yet. That's because our code doesn't do anything until we export a .swf file and play our movie. Before we do that, let's ask Flash to say hi back to us. Type your fourth line of code under the lines you've already typed (man, we're really on a roll now . . . ):

trace ("Hi there, " + firstName + ", nice to meet you.");

Figure 1-3. Flash gets friendly

1.1.3. Keeping Track of Things ( Variables)

var message = "Hi there, Flash!";

you didn't really say hi to Flash. You said something more like this:

Flash, please remember a piece of information for me -- specifically, the phrase "Hi there, Flash!" I may need that information in the future, so please give it a label called message. If I ask you for message later, give me back the text "Hi there, Flash!"

Perhaps not as friendly as saying hi, but it illustrates one of the true foundations of programming: Flash can remember something for you, provided that you label it so that it can be found later. For example, in your second line of code, we had Flash remember your first name, and we named the reference to it firstName. Flash remembered your name and displayed it in the Output window when you tested your movie.

The fact that Flash can remember things for us is crucial in programming. Flash can remember any type of data, including text (such as your name), numbers (such as 3.14159), and more complex datatypes that we'll discuss later.

1.1.4. The Wizard Behind the Curtain (the Interpreter)

Recall your first two lines of code:

var message = "Hi there, Flash!";
var firstName = "your name here";

In each of those statements, you created a variable and assigned a value to it. Your third and fourth lines, however, are a little different:

trace (message);
trace ("Hi there, " + firstName + ", nice to meet you.");

The interpreter translates your ActionScript into a language that the computer understands and uses to carry out your code. During movie playback, the interpreter is always active, dutifully attempting to understand commands you give it. If the interpreter can understand your commands, it sends them to the computer's processor for execution. If a command generates a result, the interpreter provides that response to you. If the interpreter can't understand the command, it sends you an error message. The interpreter, hence, acts like ActionScript's switchboard operator -- it's the audience you're addressing in your code and the ambassador that reports back to you from Flash.

Let's take a closer look at how the interpreter works by examining how it handles a simple trace( ) action.

Consider this command as the interpreter would:

trace ("Nice night to learn ActionScript.");

The interpreter immediately recognizes the keyword trace from its special list of legal command names. The interpreter also knows that trace( ) is used to display text in the Output window, so it also expects to be told which text to display. It finds "Nice night to learn ActionScript." between parentheses following the word trace and thinks "Aha! That's just what I need. I'll have that sent to the Output window right away!"

That's a gross oversimplification of the internal details of how a computer processor and an interpreter work, but it illustrates these points:

• The interpreter is always listening for your instructions.

• The interpreter has to read your code, letter by letter, and try to understand it. This is the same as you trying to read and understand a sentence in a book.

• The interpreter reads your ActionScript using strict rules -- if the parentheses in our trace( ) statement were missing, for example, the interpreter wouldn't be able to understand what's going on, so the command would fail.

You've only just been introduced to the interpreter, but you'll be as intimate with it as you are with a lover before too long: lots of fights, lots of yelling -- "Why aren't you listening to me?!" -- and lots of beautiful moments when you understand each other perfectly. Strangely enough, my dad always told me the best way to learn a new language is to find a lover that speaks it. May I, therefore, be the first to wish you all the best in your new relationship with the ActionScript interpreter. From now on I'll regularly refer to "the interpreter" instead of "Flash" when describing how ActionScript instructions are carried out.

1.1.5. Extra Info Required (Arguments)

command(argument);

When supplying multiple arguments to a command, separate them with commas, like this:

command(argument1, argument2, argument3);

1.1.6. ActionScript's Glue (Operators)

trace ("Hi there, " + firstName + ", nice to meet you.");

All operators link phrases of code together, manipulating those phrases in the process. Whether the phrases are text, numbers, or some other datatype, an operator nearly always performs some kind of transformation. Very commonly, operators combine two things together, as the plus operator does. But other operators compare values, assign values, facilitate logical decisions, determine datatypes, create new objects, and provide various other handy services.

trace(5 - 2);

if (3 < 300) {
  // Do something...
}

if ("a" < "z") {
  // Do something else...
}

var x = 4;
trace (typeof x);