Array Sorting

#import <Foundation/Foundation.h>

@interface Person : NSObject

@property (copy) NSString *firstName;
@property (copy) NSString *lastName;

- (instancetype)initWithFirstName:(NSString *)firstName andLastName:(NSString *)lastName;

@end

@implementation Person

- (instancetype)initWithFirstName:(NSString *)firstName andLastName:(NSString *)lastName
{
    self = [super init];
    if ( self ) {
        _firstName = [firstName copy];
        _lastName = [lastName copy];
    }
    return self;
}

- (NSString *)description
{
    return [NSString stringWithFormat:@"%@ %@", _lastName, _firstName];
}

@end

int main(int argc, const char * argv[])
{

    @autoreleasepool {

        NSArray *people = @[ [[Person alloc] initWithFirstName:@"Albert" andLastName:@"Einshtein"],
                             [[Person alloc] initWithFirstName:@"Bonapart" andLastName:@"Napoleon"],
                             [[Person alloc] initWithFirstName:@"Michail" andLastName:@"Kutozov"],
                             [[Person alloc] initWithFirstName:@"Georgiy" andLastName:@"Zhukov"],
                             [[Person alloc] initWithFirstName:@"Vladimir" andLastName:@"Nabokov"],
                             [[Person alloc] initWithFirstName:@"Yuri" andLastName:@"Nikulin"],
                             [[Person alloc] initWithFirstName:@"Friedrich" andLastName:@"Nietzsche"] ];
        
        NSLog(@"unsorted: %@", people);
        
        // Descriptors
        NSArray *sortedWithDescriptors = [people sortedArrayUsingDescriptors:@[ [NSSortDescriptor sortDescriptorWithKey:@"lastName" ascending:YES],
                                                                     [NSSortDescriptor sortDescriptorWithKey:@"firstName" ascending:YES] ]];
        NSLog(@"sortedArrayUsingDescriptors: %@", sortedWithDescriptors);
        
        // Comparator
        NSArray *sortedUsingComparator = [people sortedArrayUsingComparator:^(Person *person1, Person *person2) {
            NSComparisonResult lastNameComparison = [[person1 lastName] compare:[person2 lastName]];
            if (lastNameComparison != NSOrderedSame)
                return lastNameComparison;
            return [[person1 firstName] compare:[person2 firstName]];
        }];

        NSLog(@"sortedArrayUsingComparator: %@", sortedUsingComparator);
    }
    return 0;
}