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  • iOS 多线程GCD的基本使用

    iOS多线程简介》中提到:GCD中有2个核心概念:1、任务(执行什么操作)2、队列(用来存放任务)

    那么多线程GCD的基本使用有哪些呢?

    可以分以下多种情况:

    1、异步函数 + 并发队列

    /**
     * 异步函数 + 并发队列:可以同时开启多条线程
     */
    - (void)asyncConcurrent
    {
        // 1.创建一个并发队列
        // dispatch_queue_create(const char *label, dispatch_queue_attr_t attr);
        // label : 相当于队列的名字
        // dispatch_queue_t queue = dispatch_queue_create("com.kyle.queue", DISPATCH_QUEUE_CONCURRENT);
        
        // 1.获得全局的并发队列
        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
        
        // 2.将任务加入队列
        dispatch_async(queue, ^{
            for (NSInteger i = 0; i<3; i++) {
                NSLog(@"this is first %@",[NSThread currentThread]);
            }
        });
        dispatch_async(queue, ^{
            for (NSInteger i = 0; i<3; i++) {
                NSLog(@"this is second %@",[NSThread currentThread]);
            }
        });
        
        dispatch_async(queue, ^{
            for (NSInteger i = 0; i<3; i++) {
                NSLog(@"this is third %@",[NSThread currentThread]);
            }
        });
        
    }

    2、同步函数 + 并发队列

    /**
     * 同步函数 + 并发队列:不会开启新的线程
     */
    
    - (void)syncConcurrent
    {
        // 1.获得全局的并发队列
        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
        
        // 2.将任务加入队列
        dispatch_sync(queue, ^{
            NSLog(@"this is first %@",[NSThread currentThread]);
        });
        dispatch_sync(queue, ^{
            NSLog(@"this is second %@",[NSThread currentThread]);
        });
        dispatch_sync(queue, ^{
            NSLog(@"this is third %@",[NSThread currentThread]);
        });
        
    }

    3、异步函数 + 串行队列

    /**
     * 异步函数 + 串行队列:会开启新的线程,但是任务是串行的,执行完一个任务,再执行下一个任务
     */
    - (void)asyncSerial
    {
        // 1.创建串行队列
        dispatch_queue_t queue = dispatch_queue_create("com.kyle.queue", DISPATCH_QUEUE_SERIAL);
        //    dispatch_queue_t queue = dispatch_queue_create("com.kyle.queue", NULL);
        
        // 2.将任务加入队列
        dispatch_async(queue, ^{
            NSLog(@"this is first %@",[NSThread currentThread]);
        });
        dispatch_async(queue, ^{
            NSLog(@"this is second %@",[NSThread currentThread]);
        });
        dispatch_async(queue, ^{
            NSLog(@"this is third %@",[NSThread currentThread]);
        });
    }

    4、同步函数 + 串行队列

    /**
     * 同步函数 + 串行队列:不会开启新的线程,在当前线程执行任务。任务是串行的,执行完一个任务,再执行下一个任务
     */
    - (void)syncSerial
    {
        // 1.创建串行队列
        dispatch_queue_t queue = dispatch_queue_create("com.kyle.queue", DISPATCH_QUEUE_SERIAL);
        
        // 2.将任务加入队列
        dispatch_sync(queue, ^{
            NSLog(@"this is first %@",[NSThread currentThread]);
        });
        dispatch_sync(queue, ^{
            NSLog(@"this is second %@",[NSThread currentThread]);
        });
        dispatch_sync(queue, ^{
            NSLog(@"this is third %@",[NSThread currentThread]);
        });
    }

    5、异步函数 + 主队列

    // * 异步函数 + 主队列:只在主线程中执行任务
    
    - (void)asyncMain
    {
        // 1.获得主队列
        dispatch_queue_t  queue =  dispatch_get_main_queue();
        // 2.将任务加入队列
        dispatch_async(queue, ^{
            NSLog(@"this is first %@",[NSThread currentThread]);
            NSLog(@"this is second %@",[NSThread currentThread]);
            NSLog(@"this is third %@",[NSThread currentThread]);
        });
    }

    6、同步函数 + 主队列

    // * 同步函数 + 主队列:
    - (void)syncMain
    {
        NSLog(@"begin");
        
        // 1.获得主队列
        dispatch_queue_t queue =  dispatch_get_main_queue();
        // 2.将任务加入队列
        dispatch_sync(queue, ^{
            NSLog(@"this is %@",[NSThread currentThread]);
            
        });
        NSLog(@"end");
    }

    造成“相互等待的死锁”

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  • 原文地址:https://www.cnblogs.com/jukaiit/p/5585954.html
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