Handling duplicate entries in Core Data

Handling duplicate entries in Core Data

I have an app that allows users to save favorites. I am using Core Data to
store the favorites as managed objects. I have written some code to
prevent the possibility of storing duplicates, but am wondering if there
is a better way to do so. Each favorite object has an ID field that is
unique. In the following code I am simply looping through and checking the
ID field, and if the value already exists, setting a flag value to true,
and breaking out of the loop.
-(BOOL)addFavorite{
BOOL entityExists = NO;
if(context){
// does this favorite already exist?
NSArray *allFaves = [AppDataAccess getAllFavorites];
for(Favorite *f in allFaves){
if([f.stationIdentifier isEqualToString:stID]){
entityExists = YES;
break;
}
}
if(!entityExists){
NSError *err = nil;
Favorite *fave = [Favorite insertInManagedObjectContext:context];
fave.stationRealName = riverGauge.name;
fave.stationIdentifier = stID;
fave.stationState = @"WV";
if(![context save:&err]){
NSLog(@"ERROR: Could not save context--%@", err);
}
return YES;
}
return NO;
}
I was wondering if Core Data has the ability to check to see if an object
being added is a duplicate. Is there a predicate that can handle checking
for duplicates? THanks! V