Re: Is KVO really as complicated as I think?
Re: Is KVO really as complicated as I think?
- Subject: Re: Is KVO really as complicated as I think?
- From: Óscar Morales Vivó <email@hidden>
- Date: Tue, 27 Apr 2004 12:31:12 -0400
Basically
setKeys:(NSArray*)theKeys
triggerChangeNotificationsForDependentKey:(NSString*)theKey;
Is your best friend. Works as advertised. Use it during initialization
(I'm putting those in the +initialize method of the model class). And
enjoy.
On 27 Apr 2004, at 12:00, Steve Sims wrote:
OK gang, so I've designed my UI, and have an underlying data model
designed too.
It seems to me that all the input elements of my UI can be hooked up
to my model fairly easily using bindings. This is very useful to me
since I have some dual-control elements where I've got text and
sliders referring to the same data.
My data model isn't entirely simple though. I have a number of pieces
of data that are derived from other bits of data in my model. It
seems to me that by observing changes made to the values within my
model that directly affect the derived elements I could potentially
automatically regenerate my derived data. Sometimes this would mean
that a UI event would change a single variable that would result in a
cascade of updates to derived data.
This would seem to be the kind of thing that bindings and KVO are
supposed to do. However the documentation is making my head spin
right now, and I haven't found any sample code that does anything more
complex than really basic bindings stuff - certainly nothing where
there's a cascade of changes within a data model.
In my ideal world the way I'd make this work is when I initialize my
object I would indicate that a particular selector should be called
when one of a particular set of values is changed. Oh, and I'd be
able to do this for multiple selectors and related data sets too.
Thus I'd be able to set things up so that my desired cascades of
changes would happen.
It seems that KVO almost does this, but not quite in the way that I
want it to, and right now I'm having trouble bending my brain around
the way that KVO does things. It seems that things the KVO way are
much more complex, and to get what I want I need an extra layer of
abstraction that's not built in.
I've tried searching around for sample code that demonstrates KVO, or
articles that better explain the concept, but I'm not coming up with
anything right now. Does anyone have any pointers?
Steve
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