On Sep 27, 2011, at 12:18 , Ariel Feinerman wrote:
> So it is good news. Do -insertObject: atIndex:, -removeObject: or
> removeObjects: use KVO? I guess they do.
If you use these methods, you don't have to write any manual synchronization
code. Your original array will contain the modified contents.
However, in your case ('setContent: m_array'), KVO isn't involved. Kyle sent me
the following message off-list. I don't think he'll mind if I post it here,
since the information reflects badly on me, not on him.
On Sep 27, 2011, at 10:47 , Kyle Sluder wrote:
> You cannot KVO-observe an NSArray. -[NSArray
> addObserver:forKeyPath:options:context:] is implemented to throw an
> exception.
Well, I thought I'd run out of stupid things to say about NSArrayController,
but apparently I can still confuse myself.
As Kyle suggests, when you 'setContent:' on an array controller, it cannot
observe the array because KVO doesn't allow it, and, there just isn't a way to
update the array itself KVO compliantly. Under those circumstances, using the
NSArrayController methods ('addObject…', 'removeObject…', 'insertObject…') will
update the array properly, but updating the array directly won't cause the
array controller to notice.
Oddly, when I wrote some code to check out a couple of details, I found that:
-- when the array controller is *bound* to its content array, its 'remove:'
method works fine
-- when the array controller's "content" property is merely set to the content
array, 'remove:' does nothing
In the second case, I had a document object with an IBOutlet to the array
controller, and I set it up with [arrayController setContent: theArray]. When
my deletion button action method looked like this:
- (IBAction) deleteIt: (id) sender {
[arrayController remove: sender];
}
nothing got deleted. (And, yes, I let the app go back to the main event loop
before checking.)
When my deletion action method looked like this:
- (IBAction) deleteIt: (id) sender {
[arrayController removeObjects: [arrayController
selectedObjects]];
}
the deletion worked fine. That's in spite of the fact that 'remove:' is
documented to do what the second version does, though deferred to the next
iteration of the run loop.
Maybe I made a stupid mistake, but it's a bit puzzling.
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