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No prefetch mechanism for code-split children #34

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
What steps will reproduce the problem?
1. Define a child module
2. Set async = true
3. Set autoDisplay = true

What is the expected output? 
I want to be able to load the child module without displaying it, but not
at application start.   

What do you see instead?
Child module load only occurs only when event is passed to it, and that
always triggers start view display.

What version of the product are you using? On what operating system?
1.2.0 snapshot
multi-os (windows, mac, ubuntu)

Please provide any additional information below.
If I could temporarily disable the autoDisplay for the duration of a single
event, I could accomplish the prefetch (by defining and calling an event in
the child module that does nothing).   Better yet though, would be some
kind of "prefetch" mechanism built into the framework.

Thanks.
I love your framework!

Original issue reported on code.google.com by cainw...@gmail.com on 1 Jun 2010 at 3:30

GoogleCodeExporter commented 9 years ago 
I think here the best approach would be to set autoDisplay to false.

This way your module will still be loaded when the first event is passed to it 
but 
it won't be automatically displayed. You will then be able to prefetch data and 
when 
you're done, you can fire an event that will be forwarded to the parent module.
This event should contain one of the child module's view to ask the parent 
module to 
display it.

Original comment by plcoir...@gmail.com on 1 Jun 2010 at 10:57

GoogleCodeExporter commented 9 years ago 
Thanks for your quick response to this.

I have investigated the approach your suggesting.  It works, but has a 
significant 
draw-back.  If I disable autoDisplay, I need the child modules to forward the 
event 
to their parent for each and every event that they may receive from the parent 
to 
ensure that the module's start view is rendered.  In my application, I have a 
parent 
module with several children.  Each of these children has a series of events 
for 
performing crud operations (view, edit, etc) and other operations more specific 
to 
the data.  I am making use of the place mgtmt of mvp4g, and so it is possible 
for an 
application user to navigate directly to one of the crud events with a URL 
something 
like http://myappdomain.com/child/edit#id=123.   With autoDisplay turned on, 
"child" 
automatically gets loaded.  But with it off, "child" will only load if the 
"edit" 
event forward an event back to its parent with its view to load. 
To further complicate matters, some of my child modules have their own 
children, each 
with its own crud events.  An application user could access one of these events 
via a 
URL such as http://myappdomain.com/child/grandchild/edit#id=123, which means 
that not 
only would the "grandchild" need to forward its view to "child", but "child" 
also 
needs to forward its view.  Ultimately, the amount of additional code and 
maintenance 
required as new modules and events are added makes the performance gains I 
could get 
from prefetching modules not worth the effort.

Original comment by cainw...@gmail.com on 2 Jun 2010 at 1:41

GoogleCodeExporter commented 9 years ago 
I can see why it would be too difficult to implement.

By prefeching, what you would like to have, is to be able to load the child 
module 
code right after the main module is done loaded, so that when the user needs 
the 
child module, it's already there. Am I correct?

I don't see an easy way to do this now with autoDisplay activated. But it could 
be a 
nice feature to add, maybe for 1.3.0?

Original comment by plcoir...@gmail.com on 3 Jun 2010 at 10:33

GoogleCodeExporter commented 9 years ago 
>> By prefeching, what you would like to have, is to be able to 
>> load the child module code right after the main module is done 
>> loaded, so that when the user needs the child module, it's already 
>> there. Am I correct?

This is mostly correct.  Only I would like the child module to load at a time 
of my
choosing via an event.  That way I can load child modules at times that it 
makes the
most sense for the flow of the application.  For example, my application has 
security
built into it, and not every user gets access to every module.   So, after 
loading
the main module, displaying its UI, and determining which modules a user has 
access
too, then I would like to load the appropriate child modules.

>> I don't see an easy way to do this now with autoDisplay activated. 
>> But it could be a nice feature to add, maybe for 1.3.0?
That would be great.  Thank you.

Original comment by cainw...@gmail.com on 4 Jun 2010 at 1:39

GoogleCodeExporter commented 9 years ago 
Of course 1.2 would be better. ;)

Original comment by cainw...@gmail.com on 4 Jun 2010 at 2:01

GoogleCodeExporter commented 9 years ago 
I guess to add prefetch feature, we could have something like this:

@ChildModules( { @ChildModule( moduleClass = ChildModule1.class, prefetch=true 
)} )
public interface MainEventBus extends EventBusWithLookup {...}

This option will be useful only if autoDisplay = true & async = true. What it 
will do is that, autoDisplay event won't be fired the first time an event is 
forwarded to a child module.

I think this would fit your need, no?

I will try to have it in 1.2.0 if it doesn't impact the code too much.

Original comment by plcoir...@gmail.com on 7 Jun 2010 at 10:58

GoogleCodeExporter commented 9 years ago 
Yes. That work work great for me.  Thanks!

Original comment by cainw...@gmail.com on 8 Jun 2010 at 9:44

GoogleCodeExporter commented 9 years ago 
Sorry for not getting back to you earlier on this. This feature is not part of 
Mvp4g 1.2.0 but I think it can be done thanks to event filtering.

If you want to send an event to fetch your module without it to be 
automatically displayed you can do this:
{{{
//noEventFilter is a filter that you need to create to stop any event
//just implement EventFilter and have filterEvent always return false
//add the filter to stop all events
parentEventBus.addEventFilter(noEventFilter);

//prevent only the next event to be filtered
eventBus.setFilteringEnabledForNextOne(false);

//fetch child module
parentEventBus.eventToFetchAChildModule();

//remove the filter
parentEventBus.removeEventFilter(noEventFilter);
}}}

This way when the child module forwards the auto-display event to its parent, 
it will be ignored. Also events fired on the child event bus won't be blocked. 
You can have more information about event filtering here: 
http://code.google.com/p/mvp4g/wiki/EventBus#Event_Filtering

I think this will solve your problem, no?

Original comment by plcoir...@gmail.com on 29 Sep 2010 at 5:22

GoogleCodeExporter commented 9 years ago 
Yes.  I believe that this will do the trick.   Thank you!

Original comment by cw...@cloudsherpas.com on 30 Sep 2010 at 2:00

GoogleCodeExporter commented 9 years ago 
I'm invalidating the bug since, thanks to event filtering, you can prefetch 
module.

Original comment by plcoir...@gmail.com on 11 Nov 2010 at 11:55