Using Event Handlers

TABLE OF CONTENTS

• Understanding Event Handlers
• Setting a Variable
• Raising Audit events

Understanding Event Handlers

You use Event Handlers to make things happen after a specific event occur in your App.

You add Event Handlers to the following Components:

• Buttons
• Table fields
• Table row selection
• Forms

You set an event type, depends on the type of Component, so it may be a button click, or a table record selection.

The following operations are available to you:

• Select a Tab
• Raise an Audit Event
• Select a Page 
• Open a link
• Set a Variable

These types of operation are very common in App development, and provide you with a way to make your App interactive. 

Setting a Variable

If you configure an Event handler to set a Variable Data Set, the expression only evaluates if that event occurs.  This means that if you expression references another Data Set, it does not automatically reevaluate  if that Data Set updates.

To add an event handler that sets a Variable: 

1. Click on your Component.
2. Go to: Configuration > Event handlers.
3. Click Add handler.
   
4. Add an event handler with the following parameters:

Now, if an App User raises the event, the expression of the variable evaluates. If the variable value changes:

• Components that use the Variable Data Set obtain the new value of the variable are redrawn. So there is no need to apply any changes to your text component.
• Data Sets that use the Variable re-evaluate.

Raising Audit events

App Studio provides you with a simple way to record App usage. You record events for important actions that Users take in your App. As necessary, you create reports on App usage, or behavioral patterns within the Apps that you write. As an App Builder, you can write audit events from the App Studio. CafeX provides an audit log that you can retrieve data from using an API. 

To raise an audit event, add an event handler, and set the Action to Raise an audit event.

See also: Accessing Audit Information Programmatically