EventBusIJ

A simple synchronous Event Bus for Desktop and Web Edition Real Studio projects.

Events can be raised for any listener to handle. Messages are sent application wide in a console or desktop application, but are scoped to the current session in web applications.

How To Use

Add both the EventBusIJ module and the EventHandlerIJ interface to your project.

EventBusIJ extends Object, giving you access to the AddEventHandlerIJ, RemoveEventHandlerIJ and RaiseEventIJ methods on any object.

Use AddEventHandlerIJ to register an object (e.g. Window, Page, Class) as a listener for a type of event:

me.AddEventHandlerIJ("HelloMsgBox")

The object should implement the EventHandlerIJ interface, which means it must have a HandleEventIJ method ¹.

Function HandleEventIJ(EventType As String, Details As Variant) As Boolean
  // Part of the EventHandlerIJ interface.
  
  Select Case EventType
  Case "HelloMsgBox"
    MsgBox "HelloMsgBoxEventController caught the ""HelloMsgBox"" event."
  Case Else
    // This should never happen.
    MsgBox "Didn't handle EventType '" + EventType + "'."
  End Select
End Function

Then use RaiseEventIJ from any object to notify listeners for the event type that something has happened. Use either:

me.RaiseEventIJ("HelloMsgBox")

or

me.RaiseEventIJ("HelloMsgBox", Details)

where Details can be any value or object of any type (including dictionaries and arrays of objects or values) that the listener might need to use.

When an object goes away for any reason it's a good idea to tell EventBusIJ that the listener isn't interested in the event any longer...

me.RemoveEventHandlerIJ("HelloMsgBox")

Using RemoveEventHandlerIJ isn't strictly necessary as EventBusIJ uses weak links and cleans out references to missing listeners after every few events have been processed. However you'll save memory and cycles if you clean up after yourself. Just stick a call to RemoveEventHandlerIJ in either the Hidden, Close or Destructor events as required.

How To Get

Download, clone or fork from GitHub

git clone https://github.com/ianmjones/EventBusIJ.git

Author

Ian M. Jones
http://www.ianmjones.com
mailto:ian@ianmjones.com

License

Standard MIT license (a.k.a. do what you like with it except claim it as your own)...

Copyright (c) 2011 Ian M. Jones, IMiJ Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Version History

1.0 2012-05-28

• Initial public release.

--- EOF ---

Footnotes

1. This is by design, please don't ask for the ability to specify a handler function as EventBusIJ is intentionally simple, having one common handler function specified by an interface makes mistakes a lot less likely.
   A future version may enforce this rule, by making the AddEventHandlerIJ and RemoveEventHandlerIJ methods only available to objects implementing the EventHandlerIJ interface. ↩