Re: Design Question: Where to observe using KVO?
Re: Design Question: Where to observe using KVO?
- Subject: Re: Design Question: Where to observe using KVO?
- From: Ken Thomases <email@hidden>
- Date: Fri, 11 Jul 2008 01:34:17 -0500
On Jul 10, 2008, at 4:55 PM, Patrick Mau wrote:
I'd like to show you one ugly detail. I put all observed objects,
including their keyPath in a local NSDictionary, because I have to
remove the observers on deletion of a table row. The 'observeObject'
looks like that:
- (void)observeObject:(id)object withKeyPath:(NSString *)keyPath {
NSLog(@"start observing %p with keypath %@", object, keyPath);
[object addObserver:self forKeyPath:keyPath
options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld
context:nil];
[observers setValue:object forKeyPath:[NSString
stringWithFormat:@"%p.%@", object, keyPath]];
}
In my opinion, this is as ugly as it can possibly get.
I'm using the address of the observed object and append the keypath to
create a pseudo key for each observed instance.
I don't like that at all, but how would I be able to remove all
observers when I have to clean them up later?
Is there a better approach instead of observing every property of all
array entries?
How about a dictionary whose keys are NSValues representing the
objects? For each object, the value from the dictionary would be an
NSMutableArray whose elements are the key paths being observed on that
object.
// ...
NSValue* objectKey = [NSValue valueWithNonretainedObject:object];
NSMutableArray* keyPaths = [observers objectForKey:objectKey];
if (!keyPaths)
{
keyPaths = [NSMutableArray array];
[observers setObject:keyPaths forKey:objectKey];
}
[keyPaths addObject:keyPath];
Cheers,
Ken
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