Validator for ExtJS Checkbox

Very unfortunately ExtJS doesn’t offer a validator for its checkbox component.
Normally a validator checks whether a field is valid and takes care of displaying an error message if not. For a checkbox we would like that to happen if the checkbox is not selected.
Overriding the validate function of the checkbox we can provide such a functionality for all checkbox instances we are about to create:

The validator can be customized using the properties validateField and validateMessage.

Here’s a small code example:

Generic error handler for ExtJS

When you are doing client/server communication with ExtJS you probably run into the problem that you want to handle server side errors in a generic way.
A solution that I found is to override the handleFailure function in the class:

This handler simply is called whenever a server side failure occurs. As the Connection class handles all communication this can happen also in Ext.Ajax or In this example the error message to be displayed is retrieved from a server generated XML with the actual text being located at XPath Reason/Text.

So a server side error message might look like this: