iOS GCD初识.md

串行队列

• 串行队列：操作是按顺序执行的，并且都在同一个线程上输出
• 一个串行队列对应只有一个线程，因此同时只能执行一个操作，先追加的操作先执行。执行很多操作的时候就好像人们排队买东西一样，先来后到。

同步执行

dispatch_queue_t queue = dispatch_queue_create("com.kenan.comQueue", DISPATCH_QUEUE_SERIAL);
    //dispatch_sync::执行方式-同步步，会阻塞运行
    dispatch_sync(queue, ^{
        NSLog(@"1%@",[NSThread currentThread]);
    });
    NSLog(@"2%@",[NSThread currentThread]);
    dispatch_sync(queue, ^{
        NSLog(@"3%@",[NSThread currentThread]);
    });
    NSLog(@"4%@",[NSThread currentThread]);
    dispatch_sync(queue, ^{
        NSLog(@"5%@",[NSThread currentThread]);
    });
    NSLog(@"6%@",[NSThread currentThread]);

串行-同步Snip20200715_50.png

异步执行

dispatch_queue_t queue = dispatch_queue_create("com.kenan.comQueue", DISPATCH_QUEUE_SERIAL);
//dispatch_async:执行方式-异步，不会阻塞运行

    dispatch_async(queue, ^{
        NSLog(@"1%@",[NSThread currentThread]);
    });
    NSLog(@"2%@",[NSThread currentThread]);
    dispatch_async(queue, ^{
        NSLog(@"3%@",[NSThread currentThread]);
    });
    NSLog(@"4%@",[NSThread currentThread]);
    dispatch_async(queue, ^{
        NSLog(@"5%@",[NSThread currentThread]);
    });
    NSLog(@"6%@",[NSThread currentThread]);

串行-异步Snip20200715_51.png

并发队列

同步执行

dispatch_queue_t conccurentQueue = dispatch_queue_create("com.kenan.comQueue", DISPATCH_QUEUE_CONCURRENT);
    //dispatch_sync::执行方式-同步步，会阻塞运行。不会开辟线程。
    dispatch_sync(conccurentQueue, ^{
        NSLog(@"1%@",[NSThread currentThread]);
    });
    NSLog(@"2%@",[NSThread currentThread]);
    dispatch_sync(conccurentQueue, ^{
        NSLog(@"3%@",[NSThread currentThread]);
    });
    NSLog(@"4%@",[NSThread currentThread]);
    dispatch_sync(conccurentQueue, ^{
        NSLog(@"5%@",[NSThread currentThread]);
    });
    NSLog(@"6%@",[NSThread currentThread]);

并发同步Snip20200715_52.png

异步执行

dispatch_queue_t conccurentQueue = dispatch_queue_create("com.kenan.comQueue", DISPATCH_QUEUE_CONCURRENT);
//dispatch_async:执行方式-异步，不会阻塞运行。会开辟线程，线程数量取决于GCD
    dispatch_async(conccurentQueue, ^{
        NSLog(@"1%@",[NSThread currentThread]);
    });
    NSLog(@"2%@",[NSThread currentThread]);
    dispatch_async(conccurentQueue, ^{
        NSLog(@"3%@",[NSThread currentThread]);
    });
    NSLog(@"4%@",[NSThread currentThread]);
    dispatch_async(conccurentQueue, ^{
        NSLog(@"5%@",[NSThread currentThread]);
    });
    NSLog(@"6%@",[NSThread currentThread]);

并行-异步Snip20200715_53.png

串行队列同步/异步、并发队列同步/异步

Snip20200722_124.png