Re: [e4-dev] Annotations vs Events and when should we extend them ?

[Tom Schindl <tom.schindl@xxxxxxxxxxxxxxx>]

Hi,

First of all I think annotation should be used with great care here are
the rules I'd set out for when to use them.

* when we need to get return value e.g. to cancel something

* if the information is very tightly scoped to the information provider
  and many developers will make use it (performance!)


IMHO lifecycle is better done with annotations, instead of events and
the rest of the lifecycle is already annotation based.

A problem i have with the current annotation based system is that it is
very static - we have to invent too many different annotation.

I much more love us to have 1 annotation named @Lifecycle but allow it
to hold a meta value @Lifecycle("PROCESS_ADDITION"),
@Lifecycle("PRE_SHUTDOWN"), ... and we have another invoke on the
ContextInjectionFactory where we pass this meta value.

Such a feature would be very welcome to implement
https://bugs.eclipse.org/bugs/show_bug.cgi?id=392903 which has to based
upon annotation because we need to have a return value, and using the
event system is simply to cumbersom because the event is fired for each
and every element and the receiver has to skip the processing in 95% of
the cases (once more performance!).

Tom

Am 07.11.12 20:12, schrieb Eric Moffatt:
> 
> While looking at https://bugs.eclipse.org/bugs/show_bug.cgi?id=376821I
> realized that we should have some general guidelines for use in similar
> situations...
> 
> My general feeling is that we need to be strict(er) about annotations
> since I'm afraid that they'll get out of hand otherwise but I really
> don't have a particular metric in mind for deciding which technique we
> should use. In the case of the defect above the choice was made easier
> since it is clearly a UI Lifecycle event.
> 
> Can anybody think of a 'rule' for deciding when we should use one versus
> the other ?
> 
> Eric
> 
> 
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