多线程初认识

一、多线程的基本概念

二、NSThread

资源竞争原理图

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多条线程同时访问同一个资源     //4.做耗时操作时，多个线程访问同一个资源     self.ticketCount = 100;     self.threadA = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];     self.threadB = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];     self.threadC = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];     self.threadA.name = @"售票员A";     self.threadB.name = @"售票员B";     self.threadC.name = @"售票员C";     //启动线程     [self.threadA start];     [self.threadB start];     [self.threadC start]; //执行方法 - (void)saleTicket{     //锁：必须是全局唯一性的     //1.注意加锁的位置     //2.注意加锁的条件，多线程共享同一块资源     //3.注意加锁是需要付出代价的,需要耗费性能     //4.加锁的条件：线程同步     //如果不加锁的话就会出错         while (1) {             @synchronized (self) {             NSInteger count = self.ticketCount;             if (count > 0) {                 //耗时操作                 for (NSInteger i = 0; i< 100000; i++) {                 }                 self.ticketCount = count -1;                 NSLog(@"%@卖出去了一张票,还剩下%zd张票",  [NSThread currentThread].name,self.ticketCount);             }else{                 NSLog(@"票卖完了");                 break;             }         }     } }

 三、GCD

四、NSOperation

五、代码实例

1.NSOperation

 

 

2.GCD

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//1.异步函数+串行队列，开一条线程，队列中的任务是串行执行的 dispatch_queue_t queue = dispatch_queue_create("serial", DISPATCH_QUEUE_SERIAL);     dispatch_async(queue, ^{         NSLog(@"download1----%@",[NSThread currentThread]);     });     dispatch_async(queue, ^{         NSLog(@"download2---%@",[NSThread currentThread]);     });     dispatch_async(queue, ^{         NSLog(@"download3---%@",[NSThread currentThread]);     }); //2.异步函数+并行队列，开多条线程，队列中的任务是并行执行的 dispatch_queue_t queue = dispatch_queue_create("current", DISPATCH_QUEUE_CONCURRENT);     dispatch_async(queue, ^{         NSLog(@"download1----%@",[NSThread currentThread]);     });     dispatch_async(queue, ^{         NSLog(@"download2---%@",[NSThread currentThread]);     });     dispatch_async(queue, ^{         NSLog(@"download3---%@",[NSThread currentThread]);     }); //3.异步函数+主队列，所有任务都会在主线程中完成，不会开线程   dispatch_queue_t queue = dispatch_get_main_queue();     dispatch_async(queue, ^{         NSLog(@"download1----%@",[NSThread currentThread]);     });     dispatch_async(queue, ^{         NSLog(@"download2---%@",[NSThread currentThread]);     });     dispatch_async(queue, ^{         NSLog(@"download3---%@",[NSThread currentThread]);     }); //4.同步函数+串行队列，不会开线程，任务是串行执行的  dispatch_queue_t queue = dispatch_queue_create("seria", DISPATCH_QUEUE_SERIAL);     dispatch_sync(queue, ^{         NSLog(@"downloadload1----%@",[NSThread currentThread]);     });     dispatch_sync(queue, ^{         NSLog(@"downloadload2----%@",[NSThread currentThread]);     });     dispatch_sync(queue, ^{         NSLog(@"download3---%@",[NSThread currentThread]);     }); //5.同步函数+并行队列，不会开线程，任务是并行执行的   dispatch_queue_t queue = dispatch_queue_create("seria",DISPATCH_QUEUE_CONCURRENT);     dispatch_sync(queue, ^{         NSLog(@"download01-------%@",[NSThread currentThread]);     });     dispatch_sync(queue, ^{         NSLog(@"download02-------%@",[NSThread currentThread]);     });     dispatch_sync(queue, ^{         NSLog(@"download03-------%@",[NSThread currentThread]);     }); //6.//同步函数+主队列= 死锁，如果该线程在子线程中执行，那么所有队列就会在主线程执行     //同步函数，会崩掉     //同步函数:立刻马上执行,如果我没有执行完毕,那么后面的也别想执行     //异步函数:如果我没有执行完毕,那么后面的也可以执行 dispatch_queue_t queue = dispatch_get_main_queue();     dispatch_sync(queue, ^{         NSLog(@"download01------%@",[NSThread currentThread]);     });     dispatch_sync(queue, ^{         NSLog(@"download02------%@",[NSThread currentThread]);     });     dispatch_sync(queue, ^{         NSLog(@"download03------%@",[NSThread currentThread]);     }); //7.多线程下载图片 //1.创建子线程下载图片     //DISPATCH_QUEUE_PRIORITY_DEFAULT 0     dispatch_async(dispatch_get_global_queue(0, 0), ^{         //图片地址         NSURL *url = [NSURL URLWithString:@"http://a.hiphotos.baidu.com/zhidao/wh%3D450%2C600/sign=da0ec79c738da9774e7a8e2f8561d42f/c83d70cf3bc79f3d6842e09fbaa1cd11738b29f9.jpg"];         //转换成二进制数据         NSData *data = [NSData dataWithContentsOfURL:url];         //转换为图片         UIImage *image = [UIImage imageWithData:data];         dispatch_async(dispatch_get_main_queue(), ^{             //更新图片             self.headImageView.image = image;         });     }); //8.延时加载    //延时加载1 //    [self performSelector:@selector(task) withObject:nil afterDelay:2];     //延时加载2,用于定时器,repeats是否重复     [NSTimer scheduledTimerWithTimeInterval:3 target:self selector:@selector(task) userInfo:nil repeats:NO];     //延时加载3，GCD     dispatch_queue_t queue = dispatch_get_global_queue(0, 0);     dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), queue, ^{         NSLog(@"GCD-----%@",[NSThread currentThread]);     }); //9.栅栏函数 //栅栏函数不能使用全局并发队列     //什么是dispatch_barrier_async函数     //毫无疑问,dispatch_barrier_async函数的作用与barrier的意思相同,在进程管理中起到一个栅栏的作用,它等待所有位于barrier函数之前的操作执行完毕后执行,并且在barrier函数执行之后,barrier函数之后的操作才会得到执行,该函数需要同dispatch_queue_create函数生成的concurrent Dispatch Queue队列一起使用     //dispatch_barrier_async函数的作用     //如果是3条线程，并发执行的话，1条线程后面加栅栏函数，必须线程1执行完，才会执行线程2，3           //1.实现高效率的数据库访问和文件访问     //2.避免数据竞争 //获得全局并发队列 //    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);     dispatch_queue_t queue = dispatch_queue_create("barrier", DISPATCH_QUEUE_CONCURRENT);     //异步函数     dispatch_async(queue, ^{         for (NSInteger i = 0; i < 100; i++) {               NSLog(@"download01--%zd------%@",i,[NSThread currentThread]);         }     });     dispatch_async(queue, ^{         for (NSInteger i = 0; i < 100; i++) {               NSLog(@"download02----%zd----%@",i,[NSThread currentThread]);         }     });     //栅栏函数     dispatch_barrier_async(queue, ^{         NSLog(@"==========================");     });     dispatch_async(queue, ^{         for (NSInteger i = 0; i < 100; i++) {             NSLog(@"download03--%zd------%@",i,[NSThread currentThread]);         }     });     dispatch_async(queue, ^{         for (NSInteger i = 0; i < 100; i++) {             NSLog(@"download04----%zd----%@",i,[NSThread currentThread]);         }     }); //10.GCD的快速迭代 //1.拿到文件的路径     NSString *fromPath = @"/Users/xingzai/Desktop/Tools";     //2.获取文件的路径     NSString *toPath = @"/Users/xingzai/Desktop/Tool";     //3.得到目录下所有文件     NSArray *subPaths = [[NSFileManager defaultManager] subpathsAtPath:fromPath];     //4.count     NSInteger count = subPaths.count;     //5.执行     dispatch_apply(count, dispatch_get_global_queue(0, 0), ^(size_t index) {        //拼接全路径，文件的路径         NSString *fullPath = [fromPath stringByAppendingPathComponent:subPaths[index]];         //拼接全路径，文件剪切到的路径         NSString *toFullPath = [toPath stringByAppendingPathComponent:subPaths[index]];                   //参数一：文件的路径，参数二：文件剪切的位置         [[NSFileManager defaultManager] moveItemAtPath:fullPath toPath:toFullPath error:nil];     }); //11.创建组队列  //1.创建队列     dispatch_queue_t queue = dispatch_get_global_queue(0, 0);     //2.创建队列祖     dispatch_group_t group = dispatch_group_create();     //3.异步函数     /**1.封装对象        2.把任务添加到队列中        3.会监听执行情况，通知group      */     dispatch_group_async(group, queue, ^{         NSLog(@"1-------%@",[NSThread currentThread]);     });     dispatch_group_async(group, queue, ^{         NSLog(@"2-------%@",[NSThread currentThread]);     });     dispatch_group_async(group, queue, ^{         NSLog(@"3------%@",[NSThread currentThread]);     });     //拦截通知，当队列组所有的任务都执行完以后需要执行下面的方法     dispatch_group_notify(group, queue, ^{         NSLog(@"线程全部执行完了");     }); //12.合成对象 /**下载图片1,开子线程        下载图片2，开子线程        合成图片，并开子线程      */     //1.获取群组     dispatch_group_t group = dispatch_group_create();     //2.获取并发队列     dispatch_queue_t queue = dispatch_get_global_queue(0, 0);     //3.下载图片，开启子线程     dispatch_group_async(group, queue, ^{         NSLog(@"打印当前线程------%@",[NSThread currentThread]);         //3.1图片地址         NSURL *url = [NSURL URLWithString:@"http://www.qbaobei.com/tuku/images/13.jpg"];         //3.2下载二进制数据         NSData *data = [NSData dataWithContentsOfURL:url];         //3.3转换图片         self.imageOne = [UIImage imageWithData:data];     });     //下载图片2     dispatch_group_async(group, queue, ^{         NSLog(@"-------%@",[NSThread currentThread]);         //1.图片地址         NSURL *url = [NSURL URLWithString:@"http://pic1a.nipic.com/2008-09-19/2008919134941443_2.jpg"];         //2.下载二进制数据         NSData *data = [NSData dataWithContentsOfURL:url];         //3.转换图片         self.imageTwo = [UIImage imageWithData:data];     });     //合成图片     dispatch_group_notify(group, queue, ^{                   NSLog(@"-----------%@",[NSThread currentThread]);         //1.创建图形上下文         UIGraphicsBeginImageContext(CGSizeMake(320, 640));         //2.画图形         [self.imageOne drawInRect:CGRectMake(0, 0, 320, 320)];         self.imageOne = nil;                   [self.imageTwo drawInRect:CGRectMake(0, 320, 320, 320)];         self.imageTwo = nil;         //3.根据上下文得到一张图片         UIImage *image = UIGraphicsGetImageFromCurrentImageContext();         //4.关闭上下文         UIGraphicsEndImageContext();                   NSLog(@"%@",[NSThread currentThread]);         dispatch_async(dispatch_get_main_queue(), ^{             //更新UI             self.headImageView.image = image;         });     });     //由于dispatch_apply函数与dispatch_sync函数相同，会等待处理执行结束，因此推荐在dispatch_async函数中非同步地执行dispatch_apply函数