Forms Messaging

Overview

OpenPetra has a facility to send typed 'messages' between Forms on the client side. This Facility is called 'Forms Messaging'.

Forms Messaging is usually used in scenarios where an action in one Form should trigger an action in the other Form (e.g. data is saved in 'Form A' and 'Form B' needs to re-load that data and re-display it so it is refreshed). Example: The Partner Edit screen sends a Form Message if new Partner gets saved, and another Form Message if an existing Partners' data got saved. That Message could be listened for by arbitrary Forms and they could react appropriately.

Explanation of the Concept

There is always one 'Sending Form' and there are 0..n 'Listening Forms'.
Yes, 0 'Listening Forms' are allowed - it doesn't cause a failure - and the reason for that is that the 'Sending Form' cannot know at run time whether any of the Forms that would potentially be 'listening' for that particular 'message' are indeed instantiated at the time when the 'Sending Form' broadcasts the 'message'. Also, when a developer adds the 'broadcasting' of a 'Form Message' to a Form (and turns it into a 'Sending Form' by doing so) the developer doesn't need to implement the 'listening' for that 'Form Message' in any Form yet - no error will be caused at run time when the 'Forms Message' is 'broadcasted'. (Obviously nothing will happen in any other Form in that case, too!)

Messaging is Synchronous

Forms Messaging is synchronous, that is, 'messages' are 'broadcasted' in a synchronous manner and if a 'Listening Form' reacts to a 'message' then the 'broadcasting of that message' stops until that Form has finished whatever processing it will do in response to the 'message', then the 'broadcasting of that message' will continue to the next form, and so on.

Facilitating Classes

• The Class file for the definition of the typed 'messages' is \csharp\ICT\Petra\Client\CommonForms\FormsMessaging.cs.
  • The 'Sending Form' creates an instance of the TFormsMessage Class and specifies the kind of typed 'message' using the TFormsMessageClassEnum in the Constructor of that Class.
• The Class TFormsList found in C:\openpetraorg\trunk\csharp\ICT\Petra\Client\CommonForms\FormsList.cs has the public Method BroadcastFormMessage that is used by a 'Sending Form' to 'broadcast' a 'message'.

How-to: 'Broadcasting' of a 'Form Message'

TODO

How-to: 'Listening' for a 'Form Message' and reacting on it

TODO