Distributed Core Data - Core Data - page 192

-createChildForObject: Implementation
DistributedCDServer/AppDelegate.m
- (byref NSManagedObject*)createChildForObject:(byref NSManagedObject*)parent;
{
NSManagedObjectContext *context = [self managedObjectContext];
NSManagedObject *localParent = [context objectWithID:[parent objectID]];
NSManagedObject *object = nil;
object = [NSEntityDescription insertNewObjectForEntityForName:@ "Child"
inManagedObjectContext:context];
[object setValue:localParent forKey:@ "parent" ];
return object;
}
The -createChildForObject: implementation is similar to the -createObject implemen-
tation discussed earlier. There is one important difference, though. Since we
defined the Child entity to have a nonoptional parent property, we set it immedi-
ately while we are still on the main thread of the server. This again is a
protection against the uncontrollably multithreaded nature of distributed
objects. We could just create the Child entity and return it to the caller, but
there is a fair chance that a save will occur before the relationship is updated
on the client, and an error would result.
In addition to setting the parent property on the Child object, we also grab a
local reference to the passed-in NSManagedObject . Although I did not receive any
errors while testing this method by using the remote proxy, there is no reason
to risk it.
-objectsOfName:withPredicate: Implementation
DistributedCDServer/AppDelegate.m
- (byref NSArray*)objectsOfName:(bycopy NSString*)name
withPredicate:(bycopy NSPredicate*)predicate;
{
NSManagedObjectContext *context = [self managedObjectContext];
NSError *error = nil;
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:name
inManagedObjectContext:context]];
[request setPredicate:predicate];
NSArray *results = [context executeFetchRequest:request error:&error];
[request release], request = nil;
if (error) {
NSLog(@ "%@:%s Error on fetch %@" , [self class], __PRETTY_FUNCTION__, error);
return nil;
}
return results;
}