Object-C Sort Array of Dictionary

sortArrayOfDictionary.m

void sortArrayOfDictionary {
    NSArray *arr = [NSArray arrayWithObjects:
                    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:5], @"a", [NSNumber numberWithInt:5], @"b",nil],
                    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:6], @"a", [NSNumber numberWithInt:2], @"b",nil],
                    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:2], @"a", [NSNumber numberWithInt:7], @"b",nil],
                    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:5], @"a", [NSNumber numberWithInt:2], @"b",nil],
                    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:1], @"a", [NSNumber numberWithInt:0], @"b",nil],
                    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:5], @"a", [NSNumber numberWithInt:1], @"b",nil],
                    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:6], @"a", [NSNumber numberWithInt:1], @"b",nil],
                    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:2], @"a", [NSNumber numberWithInt:9], @"b",nil],
                    nil];
    NSLog(@"before sort the arr is:%@", arr);
    
    NSArray *sortedArray = [arr sortedArrayUsingComparator: ^(id obj1, id obj2) {
        if ( ([[obj1 objectForKey:@"a"] intValue] < [[obj2 objectForKey:@"a"] intValue]) || ([[obj1 objectForKey:@"a"] intValue] == [[obj2 objectForKey:@"a"] intValue] && [[obj1 objectForKey:@"b"] intValue] > [[obj2 objectForKey:@"b"] intValue] ) ) {
            return (NSComparisonResult)NSOrderedDescending ;
        } else {
            return (NSComparisonResult)NSOrderedAscending;
        }
    }];
    
    NSLog(@"after sort the arr is:%@", sortedArray);
    return;
}