User Guide

throw 215
throw
Availability
Flash Player 7.
Usage
throw expression
Description
Statement; generates, or throws, an error that can be handled, or caught, by a catch{} code block.
If an exception is not caught by a
catch or finally block, the string representation of the
thrown value is sent to the log file.
Typically, you throw instances of the Error class or its subclasses (see the Example section).
Parameters
expression
An ActionScript expression or object.
Example
In this example, a function named checkEmail() checks whether the string that is passed to it is
a properly formatted e-mail address. If the string does not contain an @ symbol, the function
throws an error.
function checkEmail(email:String) {
if (email.indexOf("@") == -1) {
throw new Error("Invalid email address");
}
}
checkEmail(“someuser_theirdomain.com”);
The following code then calls the checkEmail() function within a try code block. If the
email_txt string does not contain a valid e-mail address, the error message appears in a text field
(
error_txt).
try {
checkEmail("Joe Smith”);
} catch (e) {
error_txt.text = e.toString();
}
In the following example, a subclass of the Error class is thrown. The checkEmail() function is
modified to throw an instance of that subclass. (For more information, see “Creating subclasses”
on page 55.)
// Define Error subclass InvalidEmailError
// In InvalidEmailError.as:
class InvalidEmailAddress extends Error {
var message = "Invalid email address.";
}
CHAPTER 5
ActionScript Core Language Elements