[MacRuby-devel] kvo vs referenced hash

[Matt Aimonetti]

The project is a simple demo game using the same approach explained by Brian
where game items listen for notifications and update themselves based on the
notification.
For some reasons, I think it would be easier for the game controller to know
about the game items and call #update on each of them directly.

- Matt



On Tue, Sep 8, 2009 at 1:18 PM, Brian Chapados <chapbr at gmail.com> wrote:

> I am also not sure that I fully understand this scenario, but it
> doesn't appear that you would need KVO. Do the "tasks" or the "Brain"
> have any properties to observe?
>
> As Ben points out, KVO really shines when you need to keep a UI in
> sync with the state of a model.
>
> If "tasks" just need to know when the "Brain" is done thinking, I
> would just use standard notifications.
>
> NSString * const BrainFinishedThinkingNotification =
> @"BrainFinishedThinkingNotification"
>
> When the Brain has a thought... send a notification:
>
> (inside Brain class)
>
> - (void) thinkOfSomething
> {
>   // create idea
>
>  // send notification when finished
>  [[NSNotificationCenter defaultCenter]
> postNotificationName:BrainFinishedThinkingNotification
> withObject:self];
>  // (you could include extra data in a userInfo object)
> }
>
> That's it, the Brain doesn't have to know about Tasks.
>
> The task class can then register for changes, and respond to the
> notification:
>
> [[NSNotification defaultCenter] addObserver:self
> selector:@selector(brainFinishedThinking:)
> name:BrainFinishedThinkingNotification object:nil];
>
> handle them in:
> - (void) brainFinishedThinking:(NSNotification *)n
> {
>  // access the Brain if necessary
>  Brain *theBrain = (Brain *)[n object];
>
>  // do something
> }
>
> Tasks don't need an explicit reference to Brain.
>
> Brian
>
> On Sat, Sep 5, 2009 at 2:16 AM, Matt Aimonetti<mattaimonetti at gmail.com>
> wrote:
> > Hi list,
> >
> >  Coming from a Ruby background, I try to understand and pick the best
> from
> > Obj-C/Cococa and learn how to use brilliant ideas to improve my coding.
> >
> > Tonight I was working on a simple demo app to learn how things are done
> in
> > the Obj-C world and see how they would transpose to the MacRuby world.
> >
> > Everything went well until the KVO question came along.
> >
> > Let's say I have a controller that we are going to call Brain.
> > We also have a lot of simpler objects that don't do anything but having a
> > state and being displayed, we are going to call them Task instances. The
> > brain is called every X seconds to "think".
> >
> > My understanding is that an Obj-C developer would register all the tasks
> > instance with the brain using a KVO and the brain would send
> notifications
> > when it's being called to "think".  So, every time a new task is being
> > created, an observer is added on the brain with the new task key. Each
> Task
> > instance has an observeValueForKeyPath:ofObject:change:context: method
> > implemented which checks that the notification is meant for itself and if
> it
> > is, to act accordingly.
> >
> > While the concept is simple and attractive. I wonder if it wouldn't be
> > simpler to forget about kvo's and simply keep the list of registered
> tasks
> > in the brain and the brain would call the tasks directly and tell them to
> > change.
> >
> > It sounds to me that in the MacRuby world, it would be more efficient. If
> we
> > have 250 tasks for instance, when a notification is being sent, every
> single
> > task in the 250 tasks created, will receive the notification and will
> check
> > what to do with it. If we had a simple hash/dictionary in the brain, we
> > could directly find the task to handle and call it directly without
> having
> > to go through the 250.
> >
> > Am I missing something or in this specific case and because we use Ruby,
> KVO
> > aren't the way to go?
> >
> > Thanks for your help,
> >
> > - Matt
> >
> > _______________________________________________
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> > MacRuby-devel at lists.macosforge.org
> > http://lists.macosforge.org/mailman/listinfo.cgi/macruby-devel
> >
> >
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