GCDUtils.h

//
//  GCDUtils.h
//  GCD
//
//  Created by Ankit Thakur on 6/23/15.
//  Copyright (c) 2015 GCD. All rights reserved.
//

#import <Foundation/Foundation.h>

dispatch_queue_t GlobalMainQueue();

dispatch_queue_t GlobalUserInteractiveQueue(void);

dispatch_queue_t GlobalUserInitiatedQueue(void);

dispatch_queue_t GlobalUtilityQueue(void);

dispatch_queue_t GlobalBackgroundQueue(void);

@interface GCDUtils : NSObject

@end

GCDUtils.m

//
//  GCDUtils.m
//  GCD
//
//  Created by Ankit Thakur on 6/23/15.
//  Copyright (c) 2015 GCD. All rights reserved.
//

#import "GCDUtils.h"

dispatch_queue_t GlobalMainQueue()  {
    return dispatch_get_main_queue();
}

dispatch_queue_t GlobalUserInteractiveQueue(void) {
    return dispatch_get_global_queue(QOS_CLASS_USER_INTERACTIVE, 0);
}

dispatch_queue_t GlobalUserInitiatedQueue(void) {
    return dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0);
}

dispatch_queue_t GlobalUtilityQueue(void) {
    return dispatch_get_global_queue(QOS_CLASS_UTILITY, 0);
}

dispatch_queue_t GlobalBackgroundQueue(void) {
    return dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0);
}

@implementation GCDUtils

@end

Logs

2015-06-23 16:08:05.496 GCD[6663:357153] maxIndex: 15 -> queueName :GlobalBackgroundQueue
2015-06-23 16:08:05.496 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 0 for i = 0
2015-06-23 16:08:05.496 GCD[6663:357203] maxIndex: 15 -> queueName :GlobalBackgroundQueue
2015-06-23 16:08:05.496 GCD[6663:357202] maxIndex: 18 -> queueName :GlobalBackgroundQueue
2015-06-23 16:08:05.496 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 1 for i = 0
2015-06-23 16:08:05.496 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 0 for i = 1
2015-06-23 16:08:05.496 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 2 for i = 0
2015-06-23 16:08:05.496 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 0 for i = 2
2015-06-23 16:08:05.496 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 3 for i = 0
2015-06-23 16:08:05.497 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 1 for i = 1
2015-06-23 16:08:05.497 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 4 for i = 0
2015-06-23 16:08:05.497 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 1 for i = 2
2015-06-23 16:08:05.497 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 5 for i = 0
2015-06-23 16:08:05.497 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 2 for i = 1
2015-06-23 16:08:05.530 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 6 for i = 0
2015-06-23 16:08:05.530 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 2 for i = 2
2015-06-23 16:08:05.530 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 7 for i = 0
2015-06-23 16:08:05.530 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 8 for i = 0
2015-06-23 16:08:05.530 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 3 for i = 1
2015-06-23 16:08:05.530 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 9 for i = 0
2015-06-23 16:08:05.530 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 10 for i = 0
2015-06-23 16:08:05.530 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 11 for i = 0
2015-06-23 16:08:05.530 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 4 for i = 1
2015-06-23 16:08:05.531 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 12 for i = 0
2015-06-23 16:08:05.530 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 3 for i = 2
2015-06-23 16:08:05.586 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 5 for i = 1
2015-06-23 16:08:05.586 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 13 for i = 0
2015-06-23 16:08:05.586 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 4 for i = 2
2015-06-23 16:08:05.586 GCD[6663:357153] print queueName: GlobalBackgroundQueue index 14 for i = 0
2015-06-23 16:08:05.586 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 5 for i = 2
2015-06-23 16:08:05.586 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 6 for i = 1
2015-06-23 16:08:05.587 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 6 for i = 2
2015-06-23 16:08:05.587 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 7 for i = 1
2015-06-23 16:08:05.587 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 7 for i = 2
2015-06-23 16:08:05.592 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 8 for i = 2
2015-06-23 16:08:05.592 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 8 for i = 1
2015-06-23 16:08:05.592 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 9 for i = 2
2015-06-23 16:08:05.592 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 9 for i = 1
2015-06-23 16:08:05.593 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 10 for i = 2
2015-06-23 16:08:05.593 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 10 for i = 1
2015-06-23 16:08:05.593 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 11 for i = 2
2015-06-23 16:08:05.593 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 11 for i = 1
2015-06-23 16:08:05.593 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 12 for i = 2
2015-06-23 16:08:05.593 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 12 for i = 1
2015-06-23 16:08:05.593 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 13 for i = 2
2015-06-23 16:08:05.594 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 13 for i = 1
2015-06-23 16:08:05.594 GCD[6663:357203] print queueName: GlobalBackgroundQueue index 14 for i = 1
2015-06-23 16:08:05.594 GCD[6663:357202] print queueName: GlobalBackgroundQueue index 14 for i = 2
2015-06-23 16:08:05.594 GCD[6663:357153] maxIndex: 29 -> queueName :GlobalUserInitiatedQueue
2015-06-23 16:08:05.594 GCD[6663:357202] maxIndex: 29 -> queueName :GlobalUserInitiatedQueue
2015-06-23 16:08:05.594 GCD[6663:357203] maxIndex: 23 -> queueName :GlobalUserInitiatedQueue
2015-06-23 16:08:05.594 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 0 for i = 0
2015-06-23 16:08:05.594 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 0 for i = 1
2015-06-23 16:08:05.594 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 0 for i = 2
2015-06-23 16:08:05.594 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 1 for i = 0
2015-06-23 16:08:05.594 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 1 for i = 1
2015-06-23 16:08:05.594 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 1 for i = 2
2015-06-23 16:08:05.594 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 2 for i = 0
2015-06-23 16:08:05.595 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 2 for i = 1
2015-06-23 16:08:05.595 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 2 for i = 2
2015-06-23 16:08:05.595 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 3 for i = 0
2015-06-23 16:08:05.595 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 3 for i = 2
2015-06-23 16:08:05.595 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 3 for i = 1
2015-06-23 16:08:05.595 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 4 for i = 0
2015-06-23 16:08:05.595 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 4 for i = 2
2015-06-23 16:08:05.595 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 4 for i = 1
2015-06-23 16:08:05.595 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 5 for i = 0
2015-06-23 16:08:05.595 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 5 for i = 2
2015-06-23 16:08:05.597 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 6 for i = 0
2015-06-23 16:08:05.597 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 5 for i = 1
2015-06-23 16:08:05.597 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 6 for i = 2
2015-06-23 16:08:05.597 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 7 for i = 0
2015-06-23 16:08:05.597 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 6 for i = 1
2015-06-23 16:08:05.597 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 7 for i = 2
2015-06-23 16:08:05.597 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 8 for i = 0
2015-06-23 16:08:05.597 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 8 for i = 2
2015-06-23 16:08:05.597 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 7 for i = 1
2015-06-23 16:08:05.598 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 9 for i = 0
2015-06-23 16:08:05.598 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 9 for i = 2
2015-06-23 16:08:05.598 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 10 for i = 0
2015-06-23 16:08:05.598 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 8 for i = 1
2015-06-23 16:08:05.598 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 10 for i = 2
2015-06-23 16:08:05.598 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 11 for i = 0
2015-06-23 16:08:05.598 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 9 for i = 1
2015-06-23 16:08:05.598 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 12 for i = 0
2015-06-23 16:08:05.598 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 11 for i = 2
2015-06-23 16:08:05.598 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 10 for i = 1
2015-06-23 16:08:05.598 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 13 for i = 0
2015-06-23 16:08:05.598 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 12 for i = 2
2015-06-23 16:08:05.598 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 14 for i = 0
2015-06-23 16:08:05.598 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 11 for i = 1
2015-06-23 16:08:05.598 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 13 for i = 2
2015-06-23 16:08:05.598 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 15 for i = 0
2015-06-23 16:08:05.599 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 16 for i = 0
2015-06-23 16:08:05.599 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 17 for i = 0
2015-06-23 16:08:05.599 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 18 for i = 0
2015-06-23 16:08:05.599 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 12 for i = 1
2015-06-23 16:08:05.599 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 19 for i = 0
2015-06-23 16:08:05.599 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 13 for i = 1
2015-06-23 16:08:05.600 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 20 for i = 0
2015-06-23 16:08:05.600 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 14 for i = 1
2015-06-23 16:08:05.599 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 14 for i = 2
2015-06-23 16:08:05.600 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 21 for i = 0
2015-06-23 16:08:05.603 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 15 for i = 2
2015-06-23 16:08:05.603 GCD[6663:357153] print queueName: GlobalUserInitiatedQueue index 22 for i = 0
2015-06-23 16:08:05.603 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 15 for i = 1
2015-06-23 16:08:05.603 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 16 for i = 2
2015-06-23 16:08:05.603 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 16 for i = 1
2015-06-23 16:08:05.603 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 17 for i = 2
2015-06-23 16:08:05.603 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 17 for i = 1
2015-06-23 16:08:05.604 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 18 for i = 2
2015-06-23 16:08:05.604 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 18 for i = 1
2015-06-23 16:08:05.625 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 19 for i = 1
2015-06-23 16:08:05.625 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 19 for i = 2
2015-06-23 16:08:05.625 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 20 for i = 1
2015-06-23 16:08:05.625 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 20 for i = 2
2015-06-23 16:08:05.625 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 21 for i = 1
2015-06-23 16:08:05.625 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 21 for i = 2
2015-06-23 16:08:05.625 GCD[6663:357202] print queueName: GlobalUserInitiatedQueue index 22 for i = 1
2015-06-23 16:08:05.625 GCD[6663:357203] print queueName: GlobalUserInitiatedQueue index 22 for i = 2
2015-06-23 16:08:05.626 GCD[6663:357153] maxIndex: 10 -> queueName :GlobalUserInteractiveQueue
2015-06-23 16:08:05.626 GCD[6663:357202] maxIndex: 20 -> queueName :GlobalUserInteractiveQueue
2015-06-23 16:08:05.626 GCD[6663:357203] maxIndex: 14 -> queueName :GlobalUserInteractiveQueue
2015-06-23 16:08:05.626 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 0 for i = 0
2015-06-23 16:08:05.626 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 0 for i = 1
2015-06-23 16:08:05.626 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 0 for i = 2
2015-06-23 16:08:05.626 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 1 for i = 0
2015-06-23 16:08:05.626 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 1 for i = 1
2015-06-23 16:08:05.626 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 1 for i = 2
2015-06-23 16:08:05.626 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 2 for i = 0
2015-06-23 16:08:05.626 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 2 for i = 1
2015-06-23 16:08:05.626 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 2 for i = 2
2015-06-23 16:08:05.627 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 3 for i = 0
2015-06-23 16:08:05.641 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 4 for i = 0
2015-06-23 16:08:05.641 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 3 for i = 2
2015-06-23 16:08:05.641 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 5 for i = 0
2015-06-23 16:08:05.641 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 4 for i = 2
2015-06-23 16:08:05.641 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 3 for i = 1
2015-06-23 16:08:05.642 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 6 for i = 0
2015-06-23 16:08:05.642 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 5 for i = 2
2015-06-23 16:08:05.642 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 4 for i = 1
2015-06-23 16:08:05.642 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 7 for i = 0
2015-06-23 16:08:05.642 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 6 for i = 2
2015-06-23 16:08:05.658 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 8 for i = 0
2015-06-23 16:08:05.658 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 5 for i = 1
2015-06-23 16:08:05.658 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 7 for i = 2
2015-06-23 16:08:05.658 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 9 for i = 0
2015-06-23 16:08:05.658 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 8 for i = 2
2015-06-23 16:08:05.658 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 6 for i = 1
2015-06-23 16:08:05.659 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 10 for i = 0
2015-06-23 16:08:05.659 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 7 for i = 1
2015-06-23 16:08:05.659 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 9 for i = 2
2015-06-23 16:08:05.659 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 11 for i = 0
2015-06-23 16:08:05.662 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 10 for i = 2
2015-06-23 16:08:05.662 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 8 for i = 1
2015-06-23 16:08:05.662 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 12 for i = 0
2015-06-23 16:08:05.662 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 11 for i = 2
2015-06-23 16:08:05.662 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 9 for i = 1
2015-06-23 16:08:05.662 GCD[6663:357153] print queueName: GlobalUserInteractiveQueue index 13 for i = 0
2015-06-23 16:08:05.662 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 10 for i = 1
2015-06-23 16:08:05.662 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 12 for i = 2
2015-06-23 16:08:05.662 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 11 for i = 1
2015-06-23 16:08:05.663 GCD[6663:357203] print queueName: GlobalUserInteractiveQueue index 13 for i = 2
2015-06-23 16:08:05.663 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 12 for i = 1
2015-06-23 16:08:05.663 GCD[6663:357202] print queueName: GlobalUserInteractiveQueue index 13 for i = 1
2015-06-23 16:08:05.663 GCD[6663:357153] maxIndex: 29 -> queueName :GlobalUtilityQueue
2015-06-23 16:08:05.663 GCD[6663:357153] print queueName: GlobalUtilityQueue index 0 for i = 0
2015-06-23 16:08:05.663 GCD[6663:357153] print queueName: GlobalUtilityQueue index 1 for i = 0
2015-06-23 16:08:05.663 GCD[6663:357153] print queueName: GlobalUtilityQueue index 2 for i = 0
2015-06-23 16:08:05.664 GCD[6663:357153] print queueName: GlobalUtilityQueue index 3 for i = 0
2015-06-23 16:08:05.664 GCD[6663:357153] maxIndex: 20 -> queueName :GlobalUtilityQueue
2015-06-23 16:08:05.664 GCD[6663:357153] print queueName: GlobalUtilityQueue index 0 for i = 2
2015-06-23 16:08:05.664 GCD[6663:357153] print queueName: GlobalUtilityQueue index 1 for i = 2
2015-06-23 16:08:05.664 GCD[6663:357153] print queueName: GlobalUtilityQueue index 2 for i = 2
2015-06-23 16:08:05.664 GCD[6663:357153] print queueName: GlobalUtilityQueue index 3 for i = 2
2015-06-23 16:08:05.663 GCD[6663:357202] maxIndex: 4 -> queueName :GlobalUtilityQueue
2015-06-23 16:08:05.664 GCD[6663:357153] print queueName: GlobalUtilityQueue index 4 for i = 2
2015-06-23 16:08:05.664 GCD[6663:357153] print queueName: GlobalUtilityQueue index 5 for i = 2
2015-06-23 16:08:05.665 GCD[6663:357153] print queueName: GlobalUtilityQueue index 6 for i = 2
2015-06-23 16:08:05.664 GCD[6663:357202] print queueName: GlobalUtilityQueue index 0 for i = 1
2015-06-23 16:08:05.665 GCD[6663:357153] print queueName: GlobalUtilityQueue index 7 for i = 2
2015-06-23 16:08:05.665 GCD[6663:357153] print queueName: GlobalUtilityQueue index 8 for i = 2
2015-06-23 16:08:05.665 GCD[6663:357202] print queueName: GlobalUtilityQueue index 1 for i = 1
2015-06-23 16:08:05.665 GCD[6663:357153] print queueName: GlobalUtilityQueue index 9 for i = 2
2015-06-23 16:08:05.675 GCD[6663:357153] print queueName: GlobalUtilityQueue index 10 for i = 2
2015-06-23 16:08:05.675 GCD[6663:357153] print queueName: GlobalUtilityQueue index 11 for i = 2
2015-06-23 16:08:05.675 GCD[6663:357153] print queueName: GlobalUtilityQueue index 12 for i = 2
2015-06-23 16:08:05.675 GCD[6663:357153] print queueName: GlobalUtilityQueue index 13 for i = 2
2015-06-23 16:08:05.676 GCD[6663:357153] print queueName: GlobalUtilityQueue index 14 for i = 2
2015-06-23 16:08:05.676 GCD[6663:357153] print queueName: GlobalUtilityQueue index 15 for i = 2
2015-06-23 16:08:05.676 GCD[6663:357153] print queueName: GlobalUtilityQueue index 16 for i = 2
2015-06-23 16:08:05.676 GCD[6663:357153] print queueName: GlobalUtilityQueue index 17 for i = 2
2015-06-23 16:08:05.676 GCD[6663:357153] print queueName: GlobalUtilityQueue index 18 for i = 2
2015-06-23 16:08:05.676 GCD[6663:357153] print queueName: GlobalUtilityQueue index 19 for i = 2
2015-06-23 16:08:05.675 GCD[6663:357202] print queueName: GlobalUtilityQueue index 2 for i = 1
2015-06-23 16:08:05.677 GCD[6663:357202] print queueName: GlobalUtilityQueue index 3 for i = 1
2015-06-23 16:08:05.677 GCD[6663:357202] print queueName: GlobalUtilityQueue index 4 for i = 1
2015-06-23 16:08:05.677 GCD[6663:357202] print queueName: GlobalUtilityQueue index 5 for i = 1
2015-06-23 16:08:05.677 GCD[6663:357202] print queueName: GlobalUtilityQueue index 6 for i = 1
2015-06-23 16:08:05.678 GCD[6663:357202] print queueName: GlobalUtilityQueue index 7 for i = 1
2015-06-23 16:08:05.680 GCD[6663:357202] print queueName: GlobalUtilityQueue index 8 for i = 1
2015-06-23 16:08:05.681 GCD[6663:357202] print queueName: GlobalUtilityQueue index 9 for i = 1
2015-06-23 16:08:05.681 GCD[6663:357202] print queueName: GlobalUtilityQueue index 10 for i = 1
2015-06-23 16:08:05.681 GCD[6663:357202] print queueName: GlobalUtilityQueue index 11 for i = 1
2015-06-23 16:08:05.681 GCD[6663:357202] print queueName: GlobalUtilityQueue index 12 for i = 1
2015-06-23 16:08:05.681 GCD[6663:357202] print queueName: GlobalUtilityQueue index 13 for i = 1
2015-06-23 16:08:05.681 GCD[6663:357202] print queueName: GlobalUtilityQueue index 14 for i = 1
2015-06-23 16:08:05.681 GCD[6663:357202] print queueName: GlobalUtilityQueue index 15 for i = 1
2015-06-23 16:08:05.682 GCD[6663:357202] print queueName: GlobalUtilityQueue index 16 for i = 1
2015-06-23 16:08:05.682 GCD[6663:357202] print queueName: GlobalUtilityQueue index 17 for i = 1
2015-06-23 16:08:05.682 GCD[6663:357202] print queueName: GlobalUtilityQueue index 18 for i = 1
2015-06-23 16:08:05.682 GCD[6663:357202] print queueName: GlobalUtilityQueue index 19 for i = 1

ViewController.m

//
//  ViewController.m
//  GCD
//
//  Created by Ankit Thakur on 6/23/15.
//  Copyright (c) 2015 GCD. All rights reserved.
//

#import "ViewController.h"
#import "GCDUtils.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    dispatch_queue_t backgroundQueue = GlobalBackgroundQueue();
    dispatch_queue_t backgroundQueue1 = GlobalUserInitiatedQueue();
    dispatch_queue_t backgroundQueue2 = GlobalUserInteractiveQueue();
    dispatch_queue_t backgroundQueue3 = GlobalUtilityQueue();
    dispatch_queue_t backgroundQueue4 = GlobalMainQueue();
    
    [self operateQueue:backgroundQueue withName:@"GlobalBackgroundQueue"];
    [self operateQueue:backgroundQueue1 withName:@"GlobalUserInitiatedQueue"];
    [self operateQueue:backgroundQueue2 withName:@"GlobalUserInteractiveQueue"];
    [self operateQueue:backgroundQueue3 withName:@"GlobalUtilityQueue"];
    [self operateQueue:backgroundQueue4 withName:@"backgroundQueue4"];

}

- (void) operateQueue:(dispatch_queue_t)queue withName:(NSString*)queueName{
    
    __block int maxIndex = 10;
    dispatch_group_t queueDownloadGroup = dispatch_group_create();
    
    dispatch_apply(3, queue, ^(size_t i) {
        
        maxIndex = arc4random() % 30;
        
        NSLog(@"maxIndex: %d -> queueName :%@", maxIndex, queueName);
        dispatch_group_enter(queueDownloadGroup);
        int index = 0;
        while (index < maxIndex) {
            NSLog(@"print queueName: %@ index %d for i = %zu", queueName, index, i);
            index++;
        }
        dispatch_group_leave(queueDownloadGroup);
        
        
    });
    
    dispatch_group_notify(queueDownloadGroup, dispatch_get_main_queue(), ^{
        NSLog(@"group left process %@", queueName);
    });
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end