Title: Introduction to Arrays
Level: Beginner
Author: Benjie Moss
Website: www.232.info

This is the first of two tutorials focusing on the use of arrays in actionscript. Assuming no knowledge of arrays part one of this tutorial deals with methods of array creation. Part two of this tutorial deals with using ‘for’ loops to reference arrays by index number. Part three deals with manipulating arrays using two basic array methods. This tutorial is intended as an introduction to the second tutorial and does not cover everything associated with arrays. The second tutorial covers referencing arrays by content, multi-dimensional arrays and looks at array methods in more depth. This tutorial can be used with both Flash 5 and Flash MX.

Part One: Creating Arrays
Part Two: Using Arrays
Part Three: Manipulating Arrays

I'm going to get this off my chest right now: Arrays are not a handy little add-on to actionscript, if they weren't supported, someone would need to find a way of making them work. They are a key programming concept across a multitude of languages and arguably almost as significant as variables.

Officially an array is a composite datatype, but phrased simply, it's a list of information. Like a variable it can contain any legal data. In order to use it, we assign it to a variable. fig.1 shows, on it's left hand side a series of variables and on it's right hand side the array equivalent.

Just like a variable an array can be reasigned a value, so the script in fig.2 is largely pointless. Because the arrays all have the same name all this script does is change the value of the variable person, so that only the last array is the value of ‘person’ that we could subsequently refer to. It does however illustrate that there are numerous ways to create an array and populate it with elements.

Line two illustrates assigning an empty array to a variable, which would initially seem pointless, however, if you were to follow this line with some actionscript that dynamically populated the array this could be the way to go.

Line four illustrates assigning a populated array to a variable and is probably the most common form of array creation.

Line six illustrates that creating an array with empty elements is possible. If you were to test the length of this array the result would be 6, even though no data is contained within. One of the possible uses for this method of array creation is when used in conjunction with a loop that runs the length of the array (I'll be getting to that shortly).

Lines eight & nine demonstrate that it's possible to include expressions as data in an array, just as it is with variables.

Line eleven Illustrates array literals, which are my favourite. Although there's no real benefit to creating arrays in this way, when I type a lot of actionscript with a lot of brackets surrounding equations I find the square brackets stand out more easily when I've forgotten to comment my code properly.

Lines thirteen & fifteen illustrate that it is possible to nest arrays. In the example, I've used my profile as it might exist in a list of users. One would hope that any site that needs a list of users would have more than just myself registered (sad case of affairs otherwise). So the natural way to order this information would be to have an array for each user, and then store all those arrays in one large array.

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