iOS 5 Programming Cookbook

13.5. Deleting Data From Core Data

Problem

You want to delete a managed object (a row in a table) from a managed object context (your database).

Solution

Use the deleteObject: instance method of NSManagedObjectContext:

- (BOOL) application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{ [self createNewPersonWithFirstName:@"Anthony" lastName:@"Robbins" age:51]; [self createNewPersonWithFirstName:@"Richard" lastName:@"Branson" age:61]; /* Create the fetch request first */ NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; /* Here is the entity whose contents we want to read */ NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:self.managedObjectContext]; /* Tell the request that we want to read the contents of the Person entity */ [fetchRequest setEntity:entity]; NSError *requestError = nil; /* And execute the fetch request on the context */ NSArray *persons = [self.managedObjectContext executeFetchRequest:fetchRequest error:&requestError]; /* Make sure we get the array */ if ([persons count] > 0){ /* Delete the last person in the array */ Person *lastPerson = [persons lastObject]; [self.managedObjectContext deleteObject:lastPerson]; NSError *savingError = nil; if ([self.managedObjectContext save:&savingError]){ NSLog(@"Successfully deleted the last person in the array."); } else { NSLog(@"Failed to delete the last person in the array."); } } else { NSLog(@"Could not find any Person entities ...