iOS GCD筆記

串行隊(duì)列

dispatch_queue_t queue = dispatch_queue_create("testQueue", DISPATCH_QUEUE_SERIAL);

并發(fā)隊(duì)列

dispatch_queue_t queue = dispatch_queue_create("testQueue2", DISPATCH_QUEUE_CONCURRENT);

主隊(duì)列

dispatch_queue_t mainQueue = dispatch_get_main_queue();

全局并發(fā)隊(duì)列

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

同步執(zhí)行

dispatch_sync(queue, ^{
        //這里放同步執(zhí)行任務(wù)代碼
    });

異步執(zhí)行

dispatch_async(queue, ^{
        //這里放異步執(zhí)行任務(wù)代碼
    });

同步+并發(fā)隊(duì)列 = 沒有開啟新線程,串行執(zhí)行任務(wù) sync Concurrent
同步+串行隊(duì)列 = 沒有開啟新線程,串行執(zhí)行任務(wù) sync Serial

異步+并發(fā)隊(duì)列 = 有開啟新線程,并發(fā)執(zhí)行任務(wù) async Concurrent
異步+串行隊(duì)列 = 有開啟新線程(1條),串行執(zhí)行任務(wù) async Serial

同步+主隊(duì)列 = 主線程調(diào)用:死鎖 其他線程:沒有開啟新線程,串行執(zhí)行任務(wù)
異步+主隊(duì)列 = 沒有開啟新線程,串行執(zhí)行任務(wù)

同步+并發(fā)隊(duì)列(沒有開啟新線程,串行執(zhí)行任務(wù))

- (void)syncConcurrent {
    dispatch_queue_t queue = dispatch_queue_create("syncConcurrent", DISPATCH_QUEUE_CONCURRENT);
    dispatch_sync(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];//模擬耗時操作
            NSLog(@"1--%@",[NSThread currentThread]);
        }
    });
    dispatch_sync(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
    });
    dispatch_sync(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"3--%@",[NSThread currentThread]);
        }
    });
    NSLog(@"end");
}

同步+串行(沒有開啟新線程,串行執(zhí)行任務(wù))

- (void)syncSerial {
    dispatch_queue_t queue = dispatch_queue_create("syncSerial", DISPATCH_QUEUE_SERIAL);
    dispatch_sync(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
    });
    dispatch_sync(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
    });
    dispatch_sync(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"3--%@",[NSThread currentThread]);
        }
    });
    NSLog(@"end");
}

異步+并發(fā)(可開啟多個線程,任務(wù)交替(同時)執(zhí)行)

- (void)asyncConcurrent {
    dispatch_queue_t queue = dispatch_queue_create("asyncConcurrent", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
    });
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
    });
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"3--%@",[NSThread currentThread]);
        }
    });
    NSLog(@"end");
}

異步+串行(有開啟新線程(1條),串行執(zhí)行任務(wù))

- (void)asyncSerial {
    dispatch_queue_t queue = dispatch_queue_create("asyncSerial", DISPATCH_QUEUE_SERIAL);
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
    });
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
    });
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"3--%@",[NSThread currentThread]);
        }
    });
    NSLog(@"end");
}

同步執(zhí)行+主隊(duì)列(主線程調(diào)用:死鎖)

- (void)syncMain {
    dispatch_queue_t queue = dispatch_get_main_queue();
    dispatch_sync(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"3--%@",[NSThread currentThread]);
        }
    });
    NSLog(@"end");
}

同步執(zhí)行+主隊(duì)列(其他線程調(diào)用:沒有開啟新線程,串行執(zhí)行任務(wù))

- (void)syncMain2 {
    [NSThread detachNewThreadSelector:@selector(syncMain) toTarget:self withObject:nil];
}

異步執(zhí)行+主隊(duì)列(只在主線程中執(zhí)行任務(wù),執(zhí)行完一個任務(wù),再執(zhí)行下一個任務(wù))

- (void)asyncMain {
    dispatch_queue_t queue = dispatch_get_main_queue();
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"3--%@",[NSThread currentThread]);
        }
    });
    NSLog(@"end");
}

GCD線程間的通信

- (void)communication {
    //全局并發(fā)隊(duì)列
    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
    //主隊(duì)列
    dispatch_queue_t mainQueue = dispatch_get_main_queue();
    
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
        //回主線程
        dispatch_async(mainQueue, ^{
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        });
    });
}

柵欄方法 dispatch_barrier_async

- (void)barrier {
    dispatch_queue_t queue = dispatch_queue_create("testQueue", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
    });
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
    });
    
    dispatch_barrier_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"barrier--%@",[NSThread currentThread]);
        }
    });
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"3--%@",[NSThread currentThread]);
        }
    });
    dispatch_async(queue, ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"4--%@",[NSThread currentThread]);
        }
    });
}

GCD延時執(zhí)行方法: dispatch_after

- (void)after {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        //3秒后執(zhí)行
        NSLog(@"after---%@",[NSThread currentThread]);
    });
}

GCD一次性代碼

-(void)once {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        //只執(zhí)行一次的代碼(這里默認(rèn)是線程安全的)
    });
}

GCD快速迭代

-(void)apply {
    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
    NSLog(@"apply begin");
    dispatch_apply(6, queue, ^(size_t index) {
        NSLog(@"%zd---%@",index, [NSThread currentThread]);
    });
    NSLog(@"apple end");
}

GCD隊(duì)列組 dispatch_group
dispatch_group_notify(監(jiān)聽group中任務(wù)完成的狀態(tài),當(dāng)所有的任務(wù)都執(zhí)行完成后,追加任務(wù)到group中,并執(zhí)行任務(wù))

- (void)groupNotify {
    dispatch_group_t group = dispatch_group_create();
    dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
    });
    dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
    });
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"3--%@",[NSThread currentThread]);
        }
    });
}

dispatch_group_wait(暫停(阻塞)當(dāng)前線程,等待指定的group中的任務(wù)執(zhí)行完成后,才會往下繼續(xù)執(zhí)行)

- (void)groupWait {
    dispatch_group_t group = dispatch_group_create();
    dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"1--%@",[NSThread currentThread]);
        }
    });
    dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{
        for (int i = 0; i < 2; i++) {
            [NSThread sleepForTimeInterval:2];
            NSLog(@"2--%@",[NSThread currentThread]);
        }
    });
    dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
    NSLog(@"group---end");
}

線程安全,使用semaphore加鎖

- (void)initTicketStatusSave {
    semaphoreLock = dispatch_semaphore_create(1);
    self.ticketCount = 100;
    
    dispatch_queue_t queue1 = dispatch_queue_create("queue1", DISPATCH_QUEUE_SERIAL);
    dispatch_queue_t queue2 = dispatch_queue_create("queue2", DISPATCH_QUEUE_SERIAL);
    
    __weak typeof(self) weakSelf = self;
    
    dispatch_async(queue1, ^{
        [weakSelf saleTicketNotSafe];
    });
    dispatch_async(queue2, ^{
        [weakSelf saleTicketNotSafe];
    });
}
- (void)saleTicketSafe {
    while (1) {
        //加鎖
        dispatch_semaphore_wait(semaphoreLock, DISPATCH_TIME_FOREVER);
        if (self.ticketCount > 0) {
            self.ticketCount--;
            NSLog(@"%@",[NSString stringWithFormat:@"剩余票數(shù) %ld   窗口:%@",(long)self.ticketCount,[NSThread currentThread]]);
        } else {
            NSLog(@"所有票已售完");
            //相當(dāng)于解鎖
            dispatch_semaphore_signal(semaphoreLock);
            break;
        }
        //相當(dāng)于解鎖
        dispatch_semaphore_signal(semaphoreLock);
    }
}

參考:http://m.itdecent.cn/p/2d57c72016c6

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