线程、同步异步、队列

 dispatch_queue_t _serialQueue = dispatch_queue_create("gao mao a", DISPATCH_QUEUE_SERIAL);
    //(两个队列，都是同步的时候，就没什么卵用了，一个队列就够了)
    dispatch_queue_t _gaomaoa  = dispatch_queue_create("gao maoss a", DISPATCH_QUEUE_SERIAL);
    
    NSLog(@"wo ca lei ge da ye =======  1  
");
    //同步
    dispatch_async(_gaomaoa, ^{
        NSLog(@"wo ca lei ge da ye =======  2  
");
        NSLog(@"wo ca lei ge da ye =======  2  
");
        NSLog(@"wo ca lei ge da ye =======  2  
");
        NSLog(@"wo ca lei ge da ye =======  2  
");
        NSLog(@"wo ca lei ge da ye =======  2  
");
    });
    //异步
    dispatch_sync(_serialQueue, ^{
        NSLog(@"wo ca lei ge da ye =======  3  
");
        NSLog(@"wo ca lei ge da ye =======  3  
");
        NSLog(@"wo ca lei ge da ye =======  3  
");
        NSLog(@"wo ca lei ge da ye =======  3  
");
        NSLog(@"wo ca lei ge da ye =======  3  
");
    });
    
    dispatch_sync(_serialQueue, ^{
        NSLog(@"wo ca lei ge da ye =======  4  
");
        NSLog(@"wo ca lei ge da ye =======  4  
");
        NSLog(@"wo ca lei ge da ye =======  4  
");
        NSLog(@"wo ca lei ge da ye =======  4  
");
        NSLog(@"wo ca lei ge da ye =======  4  
");
    });
    
    NSLog(@"wo ca lei ge da ye =======  5  
");
    
    NSLog(@"wo ca lei ge da ye =======  6  
");

打印结果

2016-03-29 16:33:07.522 neeq_second[903:130796] wo ca lei ge da ye =======  1  

2016-03-29 16:33:07.523 neeq_second[903:130796] wo ca lei ge da ye =======  3  

2016-03-29 16:33:07.523 neeq_second[903:130815] wo ca lei ge da ye =======  2  

2016-03-29 16:33:07.523 neeq_second[903:130796] wo ca lei ge da ye =======  3  

2016-03-29 16:33:07.523 neeq_second[903:130815] wo ca lei ge da ye =======  2  

2016-03-29 16:33:07.523 neeq_second[903:130796] wo ca lei ge da ye =======  3  

2016-03-29 16:33:07.523 neeq_second[903:130815] wo ca lei ge da ye =======  2  

2016-03-29 16:33:07.523 neeq_second[903:130796] wo ca lei ge da ye =======  3  

2016-03-29 16:33:07.523 neeq_second[903:130815] wo ca lei ge da ye =======  2  

2016-03-29 16:33:07.524 neeq_second[903:130796] wo ca lei ge da ye =======  3  

2016-03-29 16:33:07.524 neeq_second[903:130815] wo ca lei ge da ye =======  2  

2016-03-29 16:33:07.524 neeq_second[903:130796] wo ca lei ge da ye =======  4  

2016-03-29 16:33:07.524 neeq_second[903:130796] wo ca lei ge da ye =======  4  

2016-03-29 16:33:07.524 neeq_second[903:130796] wo ca lei ge da ye =======  4  

2016-03-29 16:33:07.524 neeq_second[903:130796] wo ca lei ge da ye =======  4  

2016-03-29 16:33:07.525 neeq_second[903:130796] wo ca lei ge da ye =======  4  

2016-03-29 16:33:07.525 neeq_second[903:130796] wo ca lei ge da ye =======  5  

2016-03-29 16:33:07.525 neeq_second[903:130796] wo ca lei ge da ye =======  6