iOS GCD多线程

直接上代码 --> 各种线程的创立方式

    /// 创立异步队列    dispatch_queue_t async = dispatch_queue_create("async_queue", DISPATCH_QUEUE_CONCURRENT);    /// 创立同步队列    dispatch_queue_t sync = dispatch_queue_create("sync_queue", DISPATCH_QUEUE_SERIAL);            /// 创立主队列    dispatch_queue_t main_queue = dispatch_get_main_queue();        /// 全局并发队列    dispatch_queue_t global_queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);        /// 同步    dispatch_sync(global_queue, ^{            });        /// 异步    dispatch_async(global_queue, ^{            });

线程创立的6中方式

第一种 --> 同步并发(从上往下依次执行，没有开启新线程) 在当前线程中执行任务，不会开启新线程，执行完一个任务，再执行下一个任务
| 执行结果 --> 增加至主线程执行先执行begin最后执行end，依次执行

- (void)syncConcurrentThread{    NSLog(@"同步并发---begin %@",[NSThread currentThread]);    dispatch_queue_t sync = dispatch_queue_create("syncConcurrent", DISPATCH_QUEUE_CONCURRENT);    dispatch_sync(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncConcurrent = 1--%@",[NSThread currentThread]);        }    });    dispatch_sync(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncConcurrent = 2--%@",[NSThread currentThread]);        }    });    dispatch_sync(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncConcurrent = 3--%@",[NSThread currentThread]);        }    });    NSLog(@"同步并发---end %@",[NSThread currentThread]);}执行结果：同步并发---begin <NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 1--<NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 1--<NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 1--<NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 2--<NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 2--<NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 2--<NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 3--<NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 3--<NSThread: 0x600000566940>{number = 1, name = main}syncConcurrent = 3--<NSThread: 0x600000566940>{number = 1, name = main}同步并发---end <NSThread: 0x600000566940>{number = 1, name = main}

第二种 --> 异步并发(开启多个新线程，任务随机接近同时执行) 可以开启多个线程，任务同时随机执行
| 执行结果 --> 先执行主线程代码(begin，end)，在执行子线程代码，并随机执行

- (void)asyncConcurrentThread{    NSLog(@"异步并发---begin %@",[NSThread currentThread]);    dispatch_queue_t sync = dispatch_queue_create("syncConcurrent", DISPATCH_QUEUE_CONCURRENT);    dispatch_async(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncConcurrent = 1--%@",[NSThread currentThread]);        }    });    dispatch_async(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncConcurrent = 2--%@",[NSThread currentThread]);        }    });    dispatch_async(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncConcurrent = 3--%@",[NSThread currentThread]);        }    });    NSLog(@"异步并发---end %@",[NSThread currentThread]);}执行结果：异步并发---begin <NSThread: 0x600000566940>{number = 1, name = main}异步并发---end <NSThread: 0x600000566940>{number = 1, name = main}asyncConcurrent = 1--<NSThread: 0x600000538980>{number = 3, name = (null)}asyncConcurrent = 3--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncConcurrent = 2--<NSThread: 0x60000050ad40>{number = 5, name = (null)}asyncConcurrent = 1--<NSThread: 0x600000538980>{number = 3, name = (null)}asyncConcurrent = 3--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncConcurrent = 2--<NSThread: 0x60000050ad40>{number = 5, name = (null)}asyncConcurrent = 1--<NSThread: 0x600000538980>{number = 3, name = (null)}asyncConcurrent = 3--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncConcurrent = 2--<NSThread: 0x60000050ad40>{number = 5, name = (null)}

第三种 --> 同步串行 (任务依次执行，没有开启新线程) 不会开启新线程，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
| 执行结果 --> 先执行主线程的代码(begin,end)，在加入主线程依次执行

- (void)syncSerialThread{    NSLog(@"同步串行---begin %@",[NSThread currentThread]);    dispatch_queue_t sync = dispatch_queue_create("syncConcurrent", DISPATCH_QUEUE_SERIAL);    dispatch_sync(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncSerial = 1--%@",[NSThread currentThread]);        }    });    dispatch_sync(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncSerial = 2--%@",[NSThread currentThread]);        }    });    dispatch_sync(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncSerial = 3--%@",[NSThread currentThread]);        }    });    NSLog(@"同步串行---end %@",[NSThread currentThread]);}执行结果：同步串行---begin <NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 1--<NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 1--<NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 1--<NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 2--<NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 2--<NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 2--<NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 3--<NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 3--<NSThread: 0x600000566940>{number = 1, name = main}syncSerial = 3--<NSThread: 0x600000566940>{number = 1, name = main}同步串行---end <NSThread: 0x600000566940>{number = 1, name = main}

第四种 --> 异步串行 (开启一个线程) 会开启新线程，但是由于任务是串行的，执行完一个任务，再执行下一个任务
| 执行结果 --> 先执行主线程(begin,end)，而后在新的线程依次执行任务

- (void)asyncSerialThread{    NSLog(@"异步串行---begin %@",[NSThread currentThread]);    dispatch_queue_t sync = dispatch_queue_create("syncConcurrent", DISPATCH_QUEUE_SERIAL);    dispatch_async(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncSerial = 1--%@",[NSThread currentThread]);        }    });    dispatch_async(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncSerial = 2--%@",[NSThread currentThread]);        }    });    dispatch_async(sync, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncSerial = 3--%@",[NSThread currentThread]);        }    });    NSLog(@"异步串行---end %@",[NSThread currentThread]);}执行结果：异步串行---begin <NSThread: 0x600000566940>{number = 1, name = main}异步串行---end <NSThread: 0x600000566940>{number = 1, name = main}asyncSerial = 1--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncSerial = 1--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncSerial = 1--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncSerial = 2--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncSerial = 2--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncSerial = 2--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncSerial = 3--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncSerial = 3--<NSThread: 0x600000538880>{number = 4, name = (null)}asyncSerial = 3--<NSThread: 0x600000538880>{number = 4, name = (null)}

第五种 --> 同步执行 + 主队列 在主线程调用(卡死) 在其余线程调用(不会卡死，不会开启新线程，依次执行)
| 执行结果 --> 在主队列执行(卡死) 在子线程中(依次执行)

- (void)syncMainThread{    NSLog(@"同步执行 + 主队列 ---begin %@",[NSThread currentThread]);    dispatch_queue_t main_queue = dispatch_get_main_queue();    dispatch_sync(main_queue, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncMain = 1--%@",[NSThread currentThread]);        }    });    dispatch_sync(main_queue, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncMain = 2--%@",[NSThread currentThread]);        }    });    dispatch_sync(main_queue, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"syncMain = 3--%@",[NSThread currentThread]);        }    });            NSLog(@"同步执行 + 主队列 ---end %@",[NSThread currentThread]);}执行结果：---begin <NSThread: 0x6000011b6940>{number = 1, name = main}

第六种 --> 异步执行 + 主队列 在主线程中依次执行
| 执行结果 --> 先执行主线(begin,end)，而后依次执行任务

- (void)asyncMainThread{    NSLog(@"异步执行 + 主队列 ---begin %@",[NSThread currentThread]);        dispatch_queue_t main_queue = dispatch_get_main_queue();    dispatch_async(main_queue, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncMain = 1--%@",[NSThread currentThread]);        }    });    dispatch_async(main_queue, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncMain = 2--%@",[NSThread currentThread]);        }    });    dispatch_async(main_queue, ^{        for (int i = 0; i < 3; i++) {            NSLog(@"asyncMain = 3--%@",[NSThread currentThread]);        }    });    NSLog(@"异步执行 + 主队列 ---end %@",[NSThread currentThread]);}执行结果：异步执行 + 主队列 ---begin <NSThread: 0x6000018f6980>{number = 1, name = main}异步执行 + 主队列 ---end <NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 1--<NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 1--<NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 1--<NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 2--<NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 2--<NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 2--<NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 3--<NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 3--<NSThread: 0x6000018f6980>{number = 1, name = main}asyncMain = 3--<NSThread: 0x6000018f6980>{number = 1, name = main}