Hidden Command Handler Anatomy
Applies to: Windows and Web applications.
Hidden command handlers:
- Are run in the same way as other commands but do not appear on tabs or in separate windows and are hidden from the user
- Are used to perform non-visual tasks.
- For Windows applications are reusable parts with vf_ac020 set as their ancestor.
- For Web applications they are simply Visual LANSA functions.
- Have most non-visual Framework and instance list services available to them.
Structurally, Hidden Command Handlers for Windows applications are similar to Windows Command Handlers with these important differences;
- They extend the base class #VF_AC020.
- They don't use the optional method uInitialize.
- They don't use the optional method uTerminate.
- They don't listen to events.
Hidden Command Handlers for Web applications are:
- Normal Visual LANSA functions.
- They don't include visual elements such as Request or Display commands.
- They cannot signal to commands in the same business object at the same level.
- They do not listen to events.
When using hidden command handlers it is important to remember that they;
- Should always have the Default Command option set to NEVER for instance level commands or NO for business object level commands.
- Should never be used with the Hide All Other Command Tabs option set.
- Should never be attached to RAMP Destination screens.
- Should never attempt to display information to the user or interact with the user. Hidden means hidden.
Example of a Hidden Command Handler for Windows Applications
Example of a Hidden Command Handler for Web Applications