MACROMEDIA FLASH MX 2004 - ACTIONSCRIPT - Page 240

240 Chapter 12: ActionScript Dictionary
Parameters
variableName
An identifier for a variable.
type A native data type, class name that you have defined, or interface name.
functionName An identifier for a function.
parameter An identifier for a function parameter.
Description
Operator; specifies the variable type, function return type, or function parameter type. When
used in a variable declaration or assignment, this operator specifies the variable’s type; when used
in a function declaration or definition, this operator specifies the function’s return type; when
used with a function parameter in a function definition, this operator specifies the variable type
expected for that parameter.
Types are a compile-time-only feature. All types are checked at compile time, and errors are
generated when there is a mismatch. (For more information, see Appendix A, “Error Messages,”
on page 783.) Mismatches can occur during assignment operations, function calls, and class
member dereferencing using the dot (
.) operator. To avoid type mismatch errors, use explicit
typing (see “Strict data typing” on page 38).
Types that you can use include all native object types, classes and interfaces that you define, and
Void and Function (which exist only as types, not as objects). The recognized native types are
Array, Boolean, Button, Color, CustomActions, Date, Function, LoadVars, LocalConnection,
Microphone, MovieClip, NetConnection, NetStream, Number, Object, SharedObject, Sound,
String, TextField, TextFormat, Video, Void, XML, XMLNode, and XMLSocket.
Example
Usage 1: The following example declares a public variable named userName whose type is String
and assigns an empty string to it.
public var userName:String = "";
Usage 2: This example demonstrates how to specify a function’s parameter type. The following
code defines a function named
setDate() that takes a parameter named currentDate of
type
Date.
function setDate(currentDate:Date) {
this.date = currentDate;
}
Usage 3: The following code defines a function named squareRoot() that takes a parameter
named
val of the Number type and returns the square root of val, also a Number type.
function squareRoot(val:Number):Number {
return Math.sqrt(val);
}