inline below
wblakemd said the following on 08/04/2010 01:49 PM:
> Hello All,
> I think I am getting closer to being able to use m2 effectively,
> however I have some questions about filters and the duration (scope)
> of event.args variable.
>
I assume you are meaning the Event object when you refer to the
event.args variable. Is that correct?
> Both are pretty simple, but I need some clarification. It looks to me
> that filters are used for validation and decision making. Is this
> accurate? The way I am looking at it is this way:
>
> Form submit event -> form validation filter -> form listener ->
> results page
>
Yes, they can be used for validation, authentication, decision making,
etc. However just to throw my 2 cents in. Our validation doesn't take
place at the filter level (it's pushed into our model layer because we
have a validation "framework" that we use).
> Basically you have a form, it gets submitted, it goes to the filter
> for validation and if it passes validation (which would return false,
> thus stopping that event from further processing) it send the data to
> the listener event which does something and after that completes sends
> you to a results or confirmation page (depending on what you are
> trying to do).
>
Well, sort of correct. If the filter returns true, the remaining
commands in the event-handler will continue to process. If it returns
false, the remaining commands after the filter declaration do *not*
process and therefore the event-handler is short-circuited. At this
point, Mach-II will handle the next event in the queue if there any or
stop processing if there are none. So if you return false in a filter,
you have to be sure that the filter announces another event into the
event queue or the request will end.
> Well from my understanding, if the filter returns true (basically
> failing the validation) the event can announce another event which
> might be something like message about how you filled out the form
> incorrectly, etc.
>
Basically yes. However the remaining commands in the event-handler
won't be processed so the filter would have to announce another event.
> If that is true, is it possible to access the event.args structure and
> return the data to the form so the user does not have to type it all
> back in? How long does the event.args structure remain in memory?
> Does it remain until you have another event that puts data into the
> event.args structure?
>
The Event object remains for the entire request so if you announce a new
event (either <announce event="somethingCool" copyEventArgs="true"> or
announceEvent("somethingCool", event.getArgs()) ) you can copy the
current Event args into the next event. If you do a <redirect>, the
currently processing event will not be there because a redirect does a
cflocation and therefore a new request is being made. You could use
<redirect ... persist="true"> (a feature of Mach-II) to temporarily
store the event on the redirect so it's copied on the other side of the
redirect into the new request. Think of this as a "flash" scope that is
temporary (not like session or application scope which persist).
HTH,
Peter
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