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980 Chapter 2: ActionScript Language Reference
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
block, the string representation of the thrown value is
sent to the Output panel.
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”
in
Using ActionScript in Flash .)
// Define Error subclass InvalidEmailError
// In InvalidEmailError.as:
class InvalidEmailAddress extends Error {
var message = "Invalid email address.";
}
In a FLA or AS file, enter the following ActionScript in Frame 1 of the Timeline:
import InvalidEmailAddress;
function checkEmail(email:String) {
CHAPTER 2
ActionScript Language Reference