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

[Eric Moffatt <emoffatt@xxxxxxxxxx>]

Here's a redux from my perspective:

Annotated Methods:

Using 'invoke' and annotations is *required*
if there's an expected return value (a la @CanExecute...). 

It also requires some place to store
the instance of the Object to call the invoke on. Note that if there is
more than one instance being 'invoked' then it starts getting complicated
because you end up with more than one 'answer' and have to arbitrate between
them if they differ.

UILifeCycle Events:

Using events is best when there is no
requirement for information to be returned and there are an unknown number
of potential clients of the 'event'.

In the original case in the defect the
second use seems best because it's *very* likely that more than one client
may want to know when the application is 'up'. 

The Mix:

The 'Login' use case is interesting
because it would have to be done through some annotated method (most likely
in the defined LifeCycle class). Note however that each e4 app may have
different requirements as to what *it* needs; some may need log in, others
may need to define a link to a service (like the IDE connecting to the
workspace) and others may need both or something even more complex.

So what's the responsibility of the
E4Application here ? It's apparent that we need at least one 'checkpoint'
defined in out startup lifecycle and handled in the defined life cycle
class. Now it gets fuzzy...;-), do we need more than one check point ?
I'd propose 'no' but that we guarantee that past this point that IWorkbench#close()
will cleanly close the app.

Aside from the new check point method
annotation expected to be (optionally) defined in the life cycle class
we should leave it up to the application developer what other annotations
/ class instances they want and how  they're created / (re)stored,
when they are invoked...

As far as 'MenuAboutToShow' and the
other related ones it appears that they should be defined through the UIEvents
specifications as we currently do for the UILifeCycle.ACTIVATE event.

Eric

From:	Tom Schindl <tom.schindl@xxxxxxxxxxxxxxx>
To:	e4-dev@xxxxxxxxxxx
Date:	11/08/2012 09:45 AM
Subject:	Re: [e4-dev] Annotations vs Events and when should we extend them ?
Sent by:	e4-dev-bounces@xxxxxxxxxxx

---

[...]

> I also see as an advantage that the framework behavior will change
> depending on what the annotated method will return (close the window
or
> not, show the part or not etc.). I'm not sure how or if we can do
this
> using only event dispatching.
> 

No we can't veto stuff with event dispatching, i mentionned that in my
first answer, if you need to return value you have to use annotations.

We are not using it in our current lifecycle stuff but we should e.g. to
cancel the start e.g. because the login failed, ... .

Tom

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