Home → Robotlegs 1 →

Multiple framework events triggering one command

• Edit

Paul Robertson

Feb 26, 2010 @ 06:01 AM

I have a situation where, in the app startup sequence, an event triggers a command (that loads a set of data):
// in context commandMap.mapEvent(DatabaseEvent.READY, LoadContactListCommand, DatabaseEvent, true);

Later when the data set changes (an item is deleted), an event comes back that the delete succeeded, and I'm thinking of using that to trigger the re-loading of the data set:
// in context commandMap.mapEvent(CompleteEvent.DELETE_COMPLETE, LoadContactListCommand, CompleteEvent);

Also (in code I haven't added yet) when an item is edited, I'd also like to re-load the data set, so presumably I'd need another mapping:
// in context commandMap.mapEvent(CompleteEvent.EDIT_COMPLETE, LoadContactListCommand, CompleteEvent);

My question is, is it weird that I have multiple events that trigger the same command? Or does that seem like the right way to do it? Also, does it make sense to have all those mappings in the context?

What alternative approaches should I consider (i.e. how do you do this)?
For example, one alternative I've thought of is to create a "load data" event specifically for triggering the command, and just dispatch that event at times when it's needed. But then I'd need to write a set of listeners that just get the "complete" events from the services, and dispatch the "load data" event to trigger the command. Or else I could just make the various services dispatch the "load data" event instead of their separate "complete" events -- but that seems a little weird to me, like putting controller logic into the services.

Thoughts?

1. Support Staff 1 Posted by Till Schneidere... on Feb 26, 2010 @ 12:46 PM

   

   As I see it, there's nothing weird with your approach.

   Events are gestures to which commands react. It seems natural to me
   that multiple gestures might cause the same reaction, so I map the
   same command to multiple events quite often.

   hope that helps,
   till

   • Edit

2. Support Staff 2 Posted by Joel Hooks on Feb 26, 2010 @ 04:27 PM

   

   I totally agree Till. Commands encapsulate an action that should be able to be triggered from anywhere by anything as appropriate.

   • Edit

3. 3 Posted by Paul Robertson on Feb 26, 2010 @ 09:27 PM

   

   Thanks for the advice!

   • Edit