iOS 7 Programming Cookbook

18.6. Sorting Data in Core Data

Problem

You want to sort the managed objects (records) that you fetch from a managed object context (database).

Solution

Create instances of NSSortDescriptor for each attribute (column, in the database world) of an entity that has to be sorted. Add the sort descriptors to an array and assign the array to an instance of NSFetchRequest using the setSortDescriptors: instance method. In this example code, Sorting_Data_in_Core_DataAppDelegate is the class that represents the app delegate in a universal app. To understand how the Person entity is created, please refer to Recipes 18.1 and 18.2:

- (BOOL)            application:(UIApplication *)application
  didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{

    [self createNewPersonWithFirstName:@"Richard"
                              lastName:@"Branson"
                                   age:61];

    [self createNewPersonWithFirstName:@"Anthony"
                              lastName:@"Robbins"
                                   age:51];

    /* Create the fetch request first */
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]
                                    initWithEntityName:@"Person"];

    NSSortDescriptor *ageSort =
    [[NSSortDescriptor alloc] initWithKey:@"age"
                                ascending:YES];

    NSSortDescriptor *firstNameSort =
    [[NSSortDescriptor alloc] initWithKey:@"firstName"
                                ascending:YES];

    fetchRequest.sortDescriptors = @[ageSort, firstNameSort];

    NSError *requestError = nil;

    /* And execute the fetch request on the context */
    NSArray *persons =
    [self.managedObjectContext executeFetchRequest:fetchRequest
                                             error:&requestError];

    for (Person *person in persons){

        NSLog(@"First Name = %@", person