笔记-GCD相关

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ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    //GCD
    //并行(CONCURRENT)任务执行顺序是无序的,若想让某个任务先执行,用障碍block隔开,放到障碍之前;串行(SERIAL)任务执行是有序的,遵循先来后到的原则.
    dispatch_queue_t queue = dispatch_queue_create("queue1", DISPATCH_QUEUE_CONCURRENT);
    //创建一个分组
    dispatch_group_t group1 = dispatch_group_create();
    //添加任务到队列中

    dispatch_group_async(group1, queue, ^{
        NSLog(@"竹");
    });

    //障碍block,把我们的那些任务分割成两部分,障碍前和障碍后
//    dispatch_barrier_async(queue, ^{
//        for (int i = 0; i < 1; i++) {
//            NSLog(@"11111");
//        }
//    });


    dispatch_group_async(group1, queue, ^{
        NSLog(@"川");
    });

    dispatch_group_async(group1, queue, ^{
        NSLog(@"萤");
    });

    dispatch_group_async(group1, queue, ^{
        NSLog(@"火");
    });

    //可以让某一个事件重复执行
    //第一个参数:次数
    //第二个参数:所在的队列
    //第三个参数:block块
    NSArray *array = @[@"大西洋",@"太平洋",@"印度洋",@"喜洋洋"];

    dispatch_apply(4, queue, ^(size_t t) {
        NSLog(@"绿川幸 %@",array[t]);
    });

    //延迟执行
    //DISPATCH_TIME_NOW表示当前时间
    //NSEC_PER_SEC表示1秒
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(4
     * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        NSLog(@"秒速五厘米");
    });

    //默认的并行的队列(全局队列),只要前面的任务开始执行,不管是否执行完毕,直接开始下一条任务
    dispatch_queue_t queue7 = dispatch_get_global_queue(0, 0);


    dispatch_async(queue7, ^{
        NSLog(@"%@ %d 呱呱",[NSThread currentThread],[NSThread isMainThread]);
    });

    dispatch_async(queue7, ^{
        NSLog(@"%@ %d 长大",[NSThread currentThread],[NSThread isMainThread]);
    });

    dispatch_async(queue7, ^{
        NSLog(@"%@ %d 成熟",[NSThread currentThread],[NSThread isMainThread]);
    });

    dispatch_async(queue7, ^{
        NSLog(@"%@ %d 老去",[NSThread currentThread],[NSThread isMainThread]);
    });

    dispatch_async(queue7, ^{
        NSLog(@"%@ %d 逝世",[NSThread currentThread],[NSThread isMainThread]);
    });

    //串行
    dispatch_queue_t queue8 = dispatch_get_main_queue();

    dispatch_async(queue8, ^{
        NSLog(@"%@ %d 呱呱",[NSThread currentThread],[NSThread isMainThread]);
    });

    dispatch_async(queue8, ^{
        NSLog(@"%@ %d 长大",[NSThread currentThread],[NSThread isMainThread]);
    });

    dispatch_async(queue8, ^{
        NSLog(@"%@ %d 成熟",[NSThread currentThread],[NSThread isMainThread]);
    });

    dispatch_async(queue8, ^{
        NSLog(@"%@ %d 老去",[NSThread currentThread],[NSThread isMainThread]);
    });

    dispatch_async(queue8, ^{
        NSLog(@"%@ %d 逝世",[NSThread currentThread],[NSThread isMainThread]);

        //回到主线程
        [self performSelectorOnMainThread:@selector(mainThreadAction) withObject:nil waitUntilDone:YES];

    });



    // Do any additional setup after loading the view, typically from a nib.
}

-(void)mainThreadAction{
    NSLog(@"回来了 %@",[NSThread currentThread]);
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

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