axaptapedia: Event broker

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Источник: http://www.axaptapedia.com/Event_broker
==============

Summary: /* Implementaion */

==Purpose==
* To allow [http://en.wikipedia.org/wiki/Event-driven_programming event driven programming]
* To have [http://en.wikipedia.org/wiki/Loose_coupling loose coupling] between classes
* A (partial) implementation of the [http://en.wikipedia.org/wiki/Observer_pattern Observer pattern]

==Download==

==Implementaion==
Three classes are provided:

# ''SysEventListener'', which is the interface class for a "listener"
#* ''gotEvent'', which every listener must implement
# ''SysEventInfo'', which is an implementation for a listener, which simply put received information on the [[Infolog]]
#* ''main'', contains a simple test case
# ''SysEventBroker'', which client classes use to notify listeners, it implements the following methods:
#* ''addListener'', to register a lisener
#* ''removeListener'', to unregister a listener
#* ''fireEvent'', to fire an event and to notify listeners via the ''gotEvent'' method

==Global broker==
Client classes need to share the SysEventBroker instance.
A possible solution is to use the global Infolog object.

In the Info.classDeclation add:

SysEventBroker eventBroker;


Add a new method:

public SysEventBroker eventBroker()
{
if (!eventBroker)
eventBroker = SysEventBroker::construct();
return eventBroker;
}


Beware, Infolog lives at the client, all notified infomation is sent to the client.
You could make the same implementation in the Application class which lives at the server.
But you must then remember to use the same broker.

==Warning==
This is no silver bullet, do not misuse!
Do not not use when standard method calls and argument passing is the easy solution.
Do not forget to unregister the listener, even if an exception is thrown. Use try/catch!

[[Category:Development tools]]


Источник: http://www.axaptapedia.com/Event_broker