iOS 6 Programming Cookbook

15.4. Reading Data from Core Data

Problem

You want to be able to read the contents of your entities (tables) using Core Data.

Solution

Use an instance of NSFetchRequest:

- (BOOL) createNewPersonWithFirstName:(NSString *)paramFirstName
                             lastName:(NSString *)paramLastName
                                  age:(NSUInteger)paramAge{

  BOOL result = NO;

  if ([paramFirstName length] == 0 ||
      [paramLastName length] == 0){
    NSLog(@"First and Last names are mandatory.");
    return NO;
  }

  Person *newPerson = [NSEntityDescription
                       insertNewObjectForEntityForName:@"Person"
                       inManagedObjectContext:self.managedObjectContext];

  if (newPerson == nil){
    NSLog(@"Failed to create the new person.");
    return NO;
  }

  newPerson.firstName = paramFirstName;
  newPerson.lastName = paramLastName;
  newPerson.age = [NSNumber numberWithUnsignedInteger:paramAge];

  NSError *savingError = nil;

  if ([self.managedObjectContext save:&savingError]){
    return YES;
  } else {
    NSLog(@"Failed to save the new person. Error = %@", savingError);
  }

  return result;

}

- (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 ...