iOS基础深入补完计划--多线程(面试题)汇总

- (void)thread_bingfa { for (int a = 0; a < 1000; a ++) {
        [self performSelectorInBackground:@selector(aaa:) withObject:[NSNumber numberWithInt:a]];
    }
}
- (void)aaa:(NSNumber *)number { for (int a = 0; a < 100; a++) {
        sleep(1); NSLog(@"%@",number);
    }
}

self.operationQueue=[[NSOperationQueue alloc]init];
- (void)viewDidLoad {
    for (int a = 0; a < 10000; a ++) {
        [self bbb:a];
    }
}
- (void)bbb:(int)a {
        [self.operationQueue addOperationWithBlock:^{
            for (int i = 0; i < 100; i ++) {
                sleep(10);
                NSLog(@"%d",a);
            }
        }];
}

NSOperationQueue *operationQueue=[NSOperationQueue mainQueue];
    NSBlockOperation *blockOperation1=[NSBlockOperation blockOperationWithBlock:^{
        sleep(1);
        NSLog(@"下载任务--%d",1);
    }];
    for (int i=2; i< 4; ++i) {
        [blockOperation1 addExecutionBlock:^{
            sleep(1);
            NSLog(@"下载任务--%d",i);
        }];
    }
    NSBlockOperation *blockOperation2=[NSBlockOperation blockOperationWithBlock:^{
        sleep(1);
        NSLog(@"展示任务");
    }];
    [blockOperation2 addDependency:blockOperation1];
    [operationQueue addOperation:blockOperation1];
    [operationQueue addOperation:blockOperation2];

2018-03-16 16:34:02.388806+0800 test[5620:522718] 下载任务--2
2018-03-16 16:34:02.388806+0800 test[5620:522602] 下载任务--1
2018-03-16 16:34:02.388806+0800 test[5620:522717] 下载任务--3
2018-03-16 16:34:03.390790+0800 test[5620:522602] 展示任务

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self performSelectorInBackground:@selector(fun1) withObject:nil];
}
- (void)fun1 {
    //回到主线程
    [self performSelectorOnMainThread:@selector(fun2) withObject:nil waitUntilDone:nil];
}

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
dispatch_async(queue, ^{
    // 执行耗时的异步操作...
    dispatch_async(dispatch_get_main_queue(), ^{
      // 回到主线程，执行UI刷新操作
    });
});

NSOperationQueue * queue = [[NSOperationQueue alloc]init];
//切换到子线程
[queue addOperationWithBlock:^{
    [[NSOperationQueue mainQueue] addOperationWithBlock:^{
        //切换回主线程
    }];
}];

- (void)dispatch_group_test {
    dispatch_queue_t queue = dispatch_queue_create("queue_test", DISPATCH_QUEUE_CONCURRENT);
    dispatch_group_t group = dispatch_group_create();
    dispatch_group_async(group, queue, ^{
        NSLog(@"任务1——准备休眠3秒");
        sleep(3);
        NSLog(@"任务1——完成");
    });
    NSLog(@"主线程——准备休眠5秒");
    sleep(5);
    NSLog(@"主线休眠结束");
    dispatch_group_async(group, queue, ^{
        NSLog(@"任务2——准备休眠10秒");
        sleep(10);
        NSLog(@"任务2——完成");
    });
    dispatch_group_notify(group, queue, ^{
        NSLog(@"任务组完成");
    });
    NSLog(@"主线程结束");
}

//创建操作队列
NSOperationQueue *operationQueue=[[NSOperationQueue alloc]init];
//创建最后一个操作
NSBlockOperation *lastBlockOperation=[NSBlockOperation blockOperationWithBlock:^{
    sleep(1);
    NSLog(@"最后的任务");
}];
for (int i=0; i< 5-1; ++i) {
    //创建多线程操作
    NSBlockOperation *blockOperation=[NSBlockOperation blockOperationWithBlock:^{
        sleep(i);
        NSLog(@"第%d个任务",i);
    }];
    //设置依赖操作为最后一个操作
    [blockOperation addDependency:lastBlockOperation];
    [operationQueue addOperation:blockOperation];
}
//将最后一个操作加入线程队列
[operationQueue addOperation:lastBlockOperation];

//主队列--串行
dispatch_queue_t queue1 = dispatch_get_main_queue();
//自定义串行队列
dispatch_queue_t queue2 = dispatch_queue_create("test_queue", DISPATCH_QUEUE_SERIAL);

//主队列
NSOperationQueue * queue1 = [NSOperationQueue mainQueue];
//自定义队列 -- 把并发改为1
NSOperationQueue * queue2 = [[NSOperationQueue alloc]init];
queue2.maxConcurrentOperationCount = 1;

// 创建队列组
dispatch_group_t group = dispatch_group_create();
// 创建信号量，并且设置值为3
dispatch_semaphore_t semaphore = dispatch_semaphore_create(3);
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
for (int i = 0; i < 100; i++)
{
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    dispatch_group_async(group, queue, ^{
        NSLog(@"%i",i);
        sleep(2);
        // 每次发送信号则semaphore会+1，
        dispatch_semaphore_signal(semaphore);
    });
}

NSOperationQueue * queue2 = [[NSOperationQueue alloc]init];
queue2.maxConcurrentOperationCount = 3;