Flash MX 2004 Games : Art to ActionScript

Chapter 7: So what is a variable?
This would create a variable called ‘bigfeet’ and set its current value to 14. Used in this way the
variable ‘bigfeet’ would exist throughout the life of the movie. An alternative is to declare the
variable:
var bigfeet = 14;
Used in this way as soon as the script exits the value of ‘bigfeet’ is deleted. Flash MX 2004
has introduced a new concept for ActionScript and one that you are encouraged to use, strict
data typing. Strict data typing has many benefits; often a hard-to-find problem with a game can
result in confusion over the type of a variable. If you think your variable is a number and Flash
thinks it is text then testing to see if it is greater than a certain value will often fail. But if you
use strict data typing then Flash will inform you if you use the variable in a way that it is not
expecting.
1 var bigfeet:Number = 14;
2 //Try assigning a string to it
3 bigfeet = "Very big feet";
Listing 7.1
Listing 7.1 shows how to use strict data typing. The variable is declared in line 1 using the ‘var’
keyword then the variable name followed by a colon and then the data type, in this case a number.
Now Flash knows that this variable is to be used as a number. The next line starts with ‘//’ which
Flash interprets to mean that the text that follows is ignored because it is a comment. In line 3
the variable assigned a section of text, which in programming is called a string. Flash knows that a
string is not a number and when you run the movie it displays the error shown Figure 7.6 in the
Output window.
Figure 7.6 Error message displayed after using Listing 7.1
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