gcd栅栏函数

栅栏函数之前的和之后的会分开执行,dispatch_barrier_async(<#dispatch_queue_t _Nonnull queue#>, <#^(void)block#>)中的队列不能使用全局并发队列,只能自己去创建对垒,然后最为参数

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    
    //0.获得全局并发队列
    //栅栏函数不能使用全局并发队列,只能自己创建队列
    //dispatch_queue_t queue =  dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_queue_t queue = dispatch_queue_create("download", DISPATCH_QUEUE_CONCURRENT);
    
    //1.异步函数
    dispatch_async(queue, ^{
       
        for (NSInteger i = 0; i<100; i++) {
            NSLog(@"download1-%zd-%@",i,[NSThread currentThread]);
        }
        
    });
    
    dispatch_async(queue, ^{
        
        for (NSInteger i = 0; i<100; i++) {
            NSLog(@"download2-%zd-%@",i,[NSThread currentThread]);
        }
    });
    
    dispatch_async(queue, ^{
        
        for (NSInteger i = 0; i<100; i++) {
            NSLog(@"download3-%zd-%@",i,[NSThread currentThread]);
        }
    });
    
    
    
    
    //栅栏函数,只有执行了栅栏函数之后,才会执行下面的线程
    dispatch_barrier_async(queue, ^{
       
        NSLog(@"+++++++++++++++++++++++++++++");
    });
    
    dispatch_async(queue, ^{
        
        for (NSInteger i = 0; i<100; i++) {
            NSLog(@"download4-%zd-%@",i,[NSThread currentThread]);
        }
    });
    
    
    dispatch_async(queue, ^{
        
        for (NSInteger i = 0; i<100; i++) {
            NSLog(@"download5-%zd-%@",i,[NSThread currentThread]);
        }
    });
    
    dispatch_async(queue, ^{
        
        for (NSInteger i = 0; i<100; i++) {
            NSLog(@"download6-%zd-%@",i,[NSThread currentThread]);
        }
    });
}

@end