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: Sat, 29 Jul 2006 15:28:59 +0200
It's not clear exactly what you're trying to achieve, but the following is
certainly not a correct solution for anything.
I have two Core Data entities (say Person, Age), each with 0 instances to
start with. In the program, I create n instances of Person, which creates n
instances of Age. KVO is set up by:
@implementation Person
- (void) awakeFromInsert
{
// fragment
Age * myAge = [NSEntityDescription insertNewObjectForEntityForName:
@"Age" inManagedObjectContext: managedObjectContext];
[self addObserver:myAge forKeyPath:@"yearofbirth"
options:NSKeyValueObservingOptionNew context:nil]; // context set to nil
works indeed.
}
So far, so good. But when the application is quit and relaunched, the KVO
setup is lost. What I'm trying to achieve is to set it up again in
awakeFromFetch.
You've now leaked an instance of Age (you lost the reference to the one
you alloced in the first line).
Point taken. But that can be fixed.
It's not clear where fetchResults comes from.
I create an NSFetchRequest after which the results are obtained using:
fetchResults = [managedObjectContext executeFetchRequest: fetchRequest
error: &fetchError];
[myAge index]; // to get rid of the 'fault' state (!)
It's not clear why you need to "get rid of the fault state" -- fault
handling should typically be transparent.
Line removed, it's not necessary indeed.
[myAgeArray addObject: myAge];
What is myAgeArray? Is it a persistent property? You're modifying it in
a non-KVO-compliant way.
This is an attempt to retain the objects fetched using the fetchRequest. But
probably not a very good one - I need to work out the memory management
issues first.
[self addObserver: [myAgeArray lastObject]
forKeyPath:@"yearofbirth" options: NSKeyValueObservingOptionNew
context:managedObjectContext];
The context here should almost certainly not be the managed object
context.
Setting it to 'nil' works as well, as I don't use it in the
observeValueForKeyPath method.
Thanks so far,
Arthur C.
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