Core Data updating method confusing - object

Question

i want to impliment update method for my core data class, but have problem.
-(BOOL)updateFromObject:(NSPredicate *)_find ToDesire:(NSPredicate *)_desire {
NSFetchRequest *request = [[NSFetchRequest alloc]init];
[request setEntity:entitydescription];
[request setPredicate:_find];
NSError *error = nil;
NSArray *matchData = [context executeFetchRequest:request error:&error];
if (matchData.count <=0) {
NSLog(#"Nothing to do");
return NO;
}
else {
for (NSManagedObject *obj in matchData) {
/*
this is my problem
how could i update my _desire to my object
*/
}
[context save:&error];
return YES;
}
}

Answer 1

finally i do it.
-(BOOL)updateFromObject:(NSPredicate *)_find withNewData:(NSDictionary *)_data {
NSFetchRequest *request = [[NSFetchRequest alloc]init];
[request setEntity:entitydescription];
[request setPredicate:_find];
NSError *error = nil;
NSArray *matchData = [context executeFetchRequest:request error:&error];
if (matchData.count <=0) {
NSLog(#"Nothing to update");
return NO;
}
else {
for (NSManagedObject *obj in matchData) {
//obj = [[NSManagedObject alloc]];
[obj setValuesForKeysWithDictionary:_data];
}
[context save:&error];
return YES;
}
}