NSThread GCD

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线程和进程

每一个应用程序都可以看做一个进程,每一个进程可以包含多个线程,但是至少有一个线程(一般由系统默认创建)我们称之为主线程.如果想要多线程去完成多任务工作需要我们手动开辟创建子线程一般我们将耗时的操作放入子线程进行,对于UI界面的刷新,我们仍然在主线程中工作,否则会发生灵异现象

关于多线程的好处和坏处

好处:

1.使用多线程可以把程序中的耗时操作放入子线程进行后台处理,比如网络请求,图片的下载

2.发挥多核处理器的优势,让程序执行更加流畅,更加迅速用户体验好

坏处:

1.大量的线程开辟降低代码的可读性

2.线程的开辟就意味着需要更多的空间

3.在进行多线程工作,会发生多个线程对统一资源进行抢夺,发生线程安全问题

对于网络请求可以放在子线程进行操作但是对于UI界面的刷新重新赋值需要回到主线程进行

#pragma mark - 子线程开辟 第一种方式使用 NSThread    //[NSThread currentThread] 获取当前的线程    //[NSThread isMainThread] 判断当前的线程是否是主线程    NSLog(@"%@ ----- %d",[NSThread currentThread],[NSThread isMainThread]);        //1.使用类方法 开辟子线程    [NSThread detachNewThreadSelector:@selector(print1) toTarget:self withObject:nil];    [NSThread detachNewThreadSelector:@selector(print2) toTarget:self withObject:nil];        //2.创建对象 开辟子线程    NSThread *thread1 = [[NSThread alloc] initWithTarget:self selector:@selector(print1) object:nil];    NSThread *thread2 = [[NSThread alloc] initWithTarget:self selector:@selector(print2) object:nil];   //开启子线程 并执行任务    [thread1 start];    [thread2 start];

#pragma mark - 开辟子线程的 第二种方法 使用NSObject提供的方法        [self performSelectorInBackground:@selector(print1) withObject:self];    [self performSelectorInBackground:@selector(print2) withObject:self];

#pragma mark - 开辟子线程的第三种方式 NSOperationQueue    //创建任务 NSOperation    //1.使用block 创建任务    NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{        NSLog(@"%@ ------ %d 任务1",[NSThread currentThread],[NSThread isMainThread]);    }];    NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{        NSLog(@"%@ ------ %d 任务2",[NSThread currentThread],[NSThread isMainThread]);    }];        //2.使用NSInvocationOperation 创建任务    NSInvocationOperation *operation3 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(action1) object:nil];        NSInvocationOperation *operation4 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(action2) object:nil];        //创建任务队列    NSOperationQueue *queue = [[NSOperationQueue alloc] init];    //    //控制开辟线程个数//    queue.maxConcurrentOperationCount = 1;//    //    //    //添加任务//    [queue addOperation:operation1];//    [queue addOperation:operation2];//    [queue addOperation:operation3];//    [queue addOperation:operation4];        //线程重用问题    for (int i = 0; i < 20; i++) {        //创建任务        NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{            NSLog(@"%@------------------%d   任务%d",[NSThread currentThread],[NSThread isMainThread],i);        }];        //添加到任务队列        [queue addOperation:operation];    }

串行多个任务执行时,只能一个一个执行.比如,只有当第一个任务执行完,第二个才能执行,接着是第三个...

- (IBAction)serialQueue:(id)sender {        //1.系统创建串行队列    dispatch_queue_t systemQueue = dispatch_get_main_queue();    dispatch_async(systemQueue, ^{        NSLog(@"%@ --- %d  任务1",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(systemQueue, ^{        NSLog(@"%@ --- %d  任务2",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(systemQueue, ^{        NSLog(@"%@ --- %d  任务3",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(systemQueue, ^{        NSLog(@"%@ --- %d  任务4",[NSThread currentThread],[NSThread isMainThread]);    });            //2.自己创建串行队列    //第一个参数给定一个标识    //第二个参数给定当前创建队列的属性    dispatch_queue_t queue = dispatch_queue_create("com.lanou.www", DISPATCH_QUEUE_SERIAL);        //任务添加    dispatch_async(queue, ^{                NSLog(@"%@ --- %d  任务1",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(queue, ^{                NSLog(@"%@ --- %d  任务2",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(queue, ^{                NSLog(@"%@ --- %d  任务3",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(queue, ^{                NSLog(@"%@ --- %d  任务4",[NSThread currentThread],[NSThread isMainThread]);    });}

并行建议使用系统创建的

- (IBAction)concurrentQueue:(id)sender {        //1.使用系统创建的并行队列    dispatch_queue_t systemQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    //添加 任务    //第一个参数 设置优先级    //第二个参数 预留参数 当前给0    dispatch_async(systemQueue, ^{        NSLog(@"%@-----%d  任务1",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(systemQueue, ^{        NSLog(@"%@-----%d  任务2",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(systemQueue, ^{        NSLog(@"%@-----%d  任务3",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(systemQueue, ^{        NSLog(@"%@-----%d  任务4",[NSThread currentThread],[NSThread isMainThread]);    });            //2.自己创建并行队列    dispatch_queue_t myQueue = dispatch_queue_create("com.xilanhua.www", DISPATCH_QUEUE_CONCURRENT);        dispatch_async(myQueue, ^{        NSLog(@"%@-----%d  任务1",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(myQueue, ^{        NSLog(@"%@-----%d  任务2",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(myQueue, ^{        NSLog(@"%@-----%d  任务3",[NSThread currentThread],[NSThread isMainThread]);    });        dispatch_async(myQueue, ^{        NSLog(@"%@-----%d  任务4",[NSThread currentThread],[NSThread isMainThread]);    });    }//分组- (IBAction)group:(id)sender {        //创建分组    dispatch_group_t group = dispatch_group_create();        //使用系统创建并行队列    dispatch_queue_t systemQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);                //添加任务    dispatch_group_async(group, systemQueue, ^{        NSLog(@"%@-----%d  任务1",[NSThread currentThread],[NSThread isMainThread]);    });    dispatch_group_async(group, systemQueue, ^{        NSLog(@"%@-----%d  任务2",[NSThread currentThread],[NSThread isMainThread]);    });    dispatch_group_async(group, systemQueue, ^{        NSLog(@"%@-----%d  任务3",[NSThread currentThread],[NSThread isMainThread]);    });        //当分组中所有任务完成时 执行    dispatch_group_notify(group, systemQueue, ^{        NSLog(@"分组中的任务全部完成");    });    }//障碍- (IBAction)barrier:(id)sender {        //创建自己的并行队列    dispatch_queue_t myQueue = dispatch_queue_create("com.kongxincai.www", DISPATCH_QUEUE_CONCURRENT);        //加载过程    dispatch_async(myQueue, ^{        NSLog(@"A 加载...");    });    dispatch_async(myQueue, ^{        NSLog(@"B 加载...");    });    dispatch_async(myQueue, ^{        NSLog(@"C 加载...");    });            dispatch_barrier_async(myQueue, ^{        NSLog(@"全部加载完成,开始进入游戏...");    });        //进入游戏    dispatch_async(myQueue, ^{        NSLog(@"A 进入游戏");    });    dispatch_async(myQueue, ^{        NSLog(@"B 进入游戏");    });    dispatch_async(myQueue, ^{        NSLog(@"C 进入游戏");    });            dispatch_barrier_async(myQueue, ^{        NSLog(@"全部进入游戏");                //回到主线程        dispatch_async(dispatch_get_main_queue(), ^{            NSLog(@"敌军还有30秒钟到达战场,碾碎他们");        });    });        }//一次- (IBAction)once:(id)sender {    static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{        NSLog(@"First Blood!");    });}- (IBAction)buyTicket:(id)sender {        //创建并行队列    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);        for (int i = 0; i < 11; i++) {        dispatch_async(queue, ^{            [self buy];        });    }}//购买-(void)buy{        static int count = 10; //10张票    //加锁    [_lock lock];    if (count <= 0) {        NSLog(@"没票了");    }else    {    count --;//每买一次 票数-1        NSLog(@"购买第%d张票",10-count);    }    //解锁    [_lock unlock];}

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