#import "ViewController.h"

@interface ViewController ()
@property (strong, nonatomic) dispatch_queue_t queue;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    _queue =  dispatch_queue_create("queue", NULL);

   // [self withBarrier];
   // [self withDispatchGroup];
   // [self withSemaphore];
      [self withCondition];
   // [self withOperation];

}


- (id)withBarrier {

    dispatch_async(_queue, ^{

        [NSThread sleepForTimeInterval:2];
         NSLog(@"async block");

    });

     dispatch_barrier_sync(_queue, ^{
         NSLog(@"barrier");
     });

    NSLog(@"return value");
    return nil;
}


- (id)withDispatchGroup {

    dispatch_group_t group = dispatch_group_create();

    dispatch_group_async(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^ {
        [NSThread sleepForTimeInterval:2];
        NSLog(@"async block");
    });

    dispatch_group_wait(group,DISPATCH_TIME_FOREVER);

    NSLog(@"return value");

    return nil;
}


- (id)withSemaphore {

    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);

    dispatch_async(_queue, ^{

        [NSThread sleepForTimeInterval:2];
        NSLog(@"async block");
        dispatch_semaphore_signal(semaphore);
    });

    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    NSLog(@"return value");
    return nil;
}



- (id)withCondition {

    NSCondition * locker = [[NSCondition alloc]init];
    [locker lock];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [NSThread sleepForTimeInterval:2];
        NSLog(@"completion block");
        [locker signal];
    });

    [locker wait];
    [locker unlock];

    NSLog(@"return value");
    return nil;
}



- (id)withOperation {

    NSOperationQueue *queue = [[NSOperationQueue alloc] init];

    NSBlockOperation* theOperationBlock = [NSBlockOperation blockOperationWithBlock: ^{
        NSLog(@"operation block");
    }];

    [queue addOperation:theOperationBlock];
    [queue waitUntilAllOperationsAreFinished];

    NSLog(@"return value");

    return nil;
}

@end