Re: How to make KVO setup persistent?
Re: How to make KVO setup persistent?
- Subject: Re: How to make KVO setup persistent?
- From: "Arthur C." <email@hidden>
- Date: Fri, 28 Jul 2006 15:13:11 +0200
Finally I have a working solution. It sets up KVO again after application
restart. It is as follows:
@implementation Person
NSMutableArray *myAgeArray;
+(void) initialize
{
myAgeArray = [[NSMutableArray arrayWithCapacity: 5] retain]; // or any
number
}
-(void) awakeFromFetch
{
// first, fetch the 'Age' object with index equal to [self index] using
NSFetchRequest
Age * myAge = [[Age alloc] init];
myAge = [fetchResults objectAtIndex: 0]; // only one object gets
fetched
[myAge index]; // to get rid of the 'fault' state (!)
[myAgeArray addObject: myAge];
[self addObserver: [myAgeArray lastObject] forKeyPath:@"yearofbirth"
options: NSKeyValueObservingOptionNew context:managedObjectContext];
}
-(void) dealloc
{
[myAgeArray dealloc];
[super dealloc];
}
The point is that the fetched 'Age' needs to be retained, or else it will
get autoreleased and dealloced. The global array takes care of that. The
solution appears to work OK, but maybe there is a more efficient way?
I believe this problem is covered in the KVO programming Guide, where it
(only) says:
"Note: The key-value observing addObserver:forKeyPath:options:context method
does not retain the observing object or the observed objects. You need to
review your application's requirements and manage retain and release for the
observing, and observed objects."
This looks not particularly enlightening to me, so I will file a
documentation enhancement request (in particular a piece of sample code
would do well).
Thanks for your time,
Arthur C.
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