Actionscript Cookbook

11.14. Validating Form Input

Problem

You want to validate user input before allowing a form to be submitted for processing.

Solution

Write a custom validate( ) method for the Form class that checks each form element.

Discussion

ActionScript does not provide a native means by which to validate form input. However, you can add a small amount of code to the custom Form class, with which you can then quickly add validation code to any form. You should add two methods to the custom Form class and add one line of code to the existing constructor.

One method, setValidator( ), should be used to set the validators for any elements requiring validation. The method should take two parameters: the name of the form element as a string and the validator.

The validator can have one of three types of values:

true

If the Boolean true is specified, the element must contain a value. Use this for mandatory form elements.

“email”

If the string “email” is specified, the element’s value must be in the format of a valid email address.

Regular expression

If a regular expression is specified, it defines the pattern that the element value must match.

The setValidator( ) method adds new elements to an associative array in which the key is the element name and the value is the validator. You should, therefore, initialize the associative array in the constructor method.

The validate( ) method performs the validation based on the validators that have been specified using setValidator( ). The validate( ) method should ...