线程间通信/线程间发消息

1、利用最好用的GCD操作
可以取外面的值作为参数，也可以在刷新主线程用外边的参数或者Block的参数

NSString* parameter = [self getSomeParameter];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    NSString* result = [self fetchResultFromWebWithParameter:parameter];
    dispatch_async(dispatch_get_main_queue(), ^{
        [self updateUIWithResult:result];
    });
});

2、performSelector使用
//点击屏幕开始执行下载方法

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self performSelectorInBackground:@selector(download) withObject:nil];
}

//下载图片
- (void)download
{    
    // 1.图片地址
    NSString *urlStr = @"http://d.jpg";
    
    NSURL *url = [NSURL URLWithString:urlStr];
    
    // 2.根据地址下载图片的二进制数据
   
    NSData *data = [NSData dataWithContentsOfURL:url];
    NSLog(@"---end");
    
    // 3.设置图片
    UIImage *image = [UIImage imageWithData:data];
    
    // 4.回到主线程，刷新UI界面(为了线程安全)
    [self performSelectorOnMainThread:@selector(downloadFinished:) withObject:image waitUntilDone:NO];
    
   // [self performSelector:@selector(downloadFinished:) onThread:[NSThread mainThread] withObject:image waitUntilDone:YES];
    
    
}

- (void)downloadFinished:(UIImage *)image
{
    self.imageView.image = image;
    
    NSLog(@"downloadFinished---%@", [NSThread currentThread]);
}

3、oprationQue操作

// 1.创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc]init];

    // 2.添加操作
    [queue addOperationWithBlock:^{
        // 异步进行耗时操作
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2]; // 模拟耗时操作
            NSLog(@"1---%@", [NSThread currentThread]); // 打印当前线程
        }

        // 回到主线程
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            // 进行一些 UI 刷新等操作
            for (int i = 0; i < 2; i++) {
                [NSThread sleepForTimeInterval:2]; // 模拟耗时操作
                NSLog(@"2---%@", [NSThread currentThread]); // 打印当前线程
            }
        }];
    }];

文章为学习使用，借鉴网络，如有问题请私聊