iOS 多线程的简单理解（2） 队列 ：串行 ，并行，MainQueue，GlobalQueue
多线程队列是装载线程任务的队形结构。(系统以先进先出的方式调度队列中的任务执行 FIFO)。在GCD中有两种队列：
串行队列、并发队列。
队列 ：串行队列、并发队列，全局主对列，全局并发队列
2.1. 串行队列：线程只能依次有序的执行。
2.1.1 串行方法 1
- (void)SerialQueueOne{
NSLog(@"串行1 start ：：：%@",[NSThread currentThread]);
dispatch_queue_t queue = dispatch_queue_create("test", DISPATCH_QUEUE_SERIAL);
dispatch_sync(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"串行1 index %d ::: %@",i,[NSThread currentThread]);
}
});
dispatch_sync(queue, ^{
for (int i = 10; i < 13; i++) {
NSLog(@"串行1 index %d ::: %@",i,[NSThread currentThread]);
}
});
NSLog(@"串行1 end ：：：%@",[NSThread currentThread]);
}
执行结果：：：
2017-12-20 13:49:47.427330+0800 DeadThread[8972:2450330] 串行1 start ：：：<NSThread: 0x60800006ae80>{number = 1, name = main}
2017-12-20 13:49:47.427470+0800 DeadThread[8972:2450330] 串行1 index 0 ::: <NSThread: 0x60800006ae80>{number = 1, name = main}
2017-12-20 13:49:47.427567+0800 DeadThread[8972:2450330] 串行1 index 1 ::: <NSThread: 0x60800006ae80>{number = 1, name = main}
2017-12-20 13:49:47.427636+0800 DeadThread[8972:2450330] 串行1 index 2 ::: <NSThread: 0x60800006ae80>{number = 1, name = main}
2017-12-20 13:49:47.427696+0800 DeadThread[8972:2450330] 串行1 index 10 ::: <NSThread: 0x60800006ae80>{number = 1, name = main}
2017-12-20 13:49:47.427819+0800 DeadThread[8972:2450330] 串行1 index 11 ::: <NSThread: 0x60800006ae80>{number = 1, name = main}
2017-12-20 13:49:47.427893+0800 DeadThread[8972:2450330] 串行1 index 12 ::: <NSThread: 0x60800006ae80>{number = 1, name = main}
2017-12-20 13:49:47.427966+0800 DeadThread[8972:2450330] 串行1 end ：：：<NSThread: 0x60800006ae80>{number = 1, name = main}
得到结果：：：
1.代码顺序 执行；
2.1.2 串行方法 2
- (void)SerialQueueTwo{
NSLog(@"串行2 start ：：：%@",[NSThread currentThread]);
dispatch_queue_t queue = dispatch_queue_create("test", DISPATCH_QUEUE_SERIAL);
dispatch_async(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"串行2 index %d ::: %@",i,[NSThread currentThread]);
}
});
dispatch_async(queue, ^{
for (int i = 10; i < 13; i++) {
NSLog(@"串行2 index %d ::: %@",i,[NSThread currentThread]);
}
});
NSLog(@"串行2 end ：：：%@",[NSThread currentThread]);
}
执行结果：：：
2017-12-20 13:50:47.130380+0800 DeadThread[8993:2458517] 串行1 start ：：：<NSThread: 0x60c000071300>{number = 1, name = main}
2017-12-20 13:50:47.130533+0800 DeadThread[8993:2458517] 串行1 index 0 ::: <NSThread: 0x60c000071300>{number = 1, name = main}
2017-12-20 13:50:47.130648+0800 DeadThread[8993:2458517] 串行1 index 1 ::: <NSThread: 0x60c000071300>{number = 1, name = main}
2017-12-20 13:50:47.130724+0800 DeadThread[8993:2458517] 串行1 index 2 ::: <NSThread: 0x60c000071300>{number = 1, name = main}
2017-12-20 13:50:47.130896+0800 DeadThread[8993:2458517] 串行1 index 10 ::: <NSThread: 0x60c000071300>{number = 1, name = main}
2017-12-20 13:50:47.130979+0800 DeadThread[8993:2458517] 串行1 index 11 ::: <NSThread: 0x60c000071300>{number = 1, name = main}
2017-12-20 13:50:47.131057+0800 DeadThread[8993:2458517] 串行1 index 12 ::: <NSThread: 0x60c000071300>{number = 1, name = main}
2017-12-20 13:50:47.131130+0800 DeadThread[8993:2458517] 串行1 end ：：：<NSThread: 0x60c000071300>{number = 1, name = main}
得到结果：：：
1.没有开启线程
2.代码顺序执行；
2.2 并发队列：线程可以同时一起进行执行。实际上是CPU在多条线程之间快速的切换。（并发功能只有在异步（dispatch_async）函数下才有效）
2.2.1 并发方法 1
- (void)concurrentQueueOne{
NSLog(@"并发1 start ：：：%@",[NSThread currentThread]);
dispatch_queue_t queue = dispatch_queue_create("test", DISPATCH_QUEUE_CONCURRENT);
dispatch_sync(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"并发1 index %d ::: %@",i,[NSThread currentThread]);
}
});
dispatch_sync(queue, ^{
for (int i = 10; i < 13; i++) {
NSLog(@"并发1 index %d ::: %@",i,[NSThread currentThread]);
}
});
NSLog(@"并发1 end ：：：%@",[NSThread currentThread]);
}
执行结果：：：
2017-12-20 13:52:37.606997+0800 DeadThread[9023:2470506] 并发1 start ：：：<NSThread: 0x608000261600>{number = 1, name = main}
2017-12-20 13:52:37.607130+0800 DeadThread[9023:2470506] 并发1 index 0 ::: <NSThread: 0x608000261600>{number = 1, name = main}
2017-12-20 13:52:37.607197+0800 DeadThread[9023:2470506] 并发1 index 1 ::: <NSThread: 0x608000261600>{number = 1, name = main}
2017-12-20 13:52:37.607447+0800 DeadThread[9023:2470506] 并发1 index 2 ::: <NSThread: 0x608000261600>{number = 1, name = main}
2017-12-20 13:52:37.607685+0800 DeadThread[9023:2470506] 并发1 index 10 ::: <NSThread: 0x608000261600>{number = 1, name = main}
2017-12-20 13:52:37.607891+0800 DeadThread[9023:2470506] 并发1 index 11 ::: <NSThread: 0x608000261600>{number = 1, name = main}
2017-12-20 13:52:37.608056+0800 DeadThread[9023:2470506] 并发1 index 12 ::: <NSThread: 0x608000261600>{number = 1, name = main}
2017-12-20 13:52:37.608190+0800 DeadThread[9023:2470506] 并发1 end ：：：<NSThread: 0x608000261600>{number = 1, name = main}
得到结果：：：
1.线程顺序执行
2.2.2 并发方法 2
- (void)concurrentQueueTwo{
NSLog(@"并发2 start ：：：%@",[NSThread currentThread]);
dispatch_queue_t queue = dispatch_queue_create("test", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"并发2 index %d ::: %@",i,[NSThread currentThread]);
}
});
dispatch_async(queue, ^{
for (int i = 10; i < 13; i++) {
NSLog(@"并发2 index %d ::: %@",i,[NSThread currentThread]);
}
});
NSLog(@"并发2 end ：：：%@",[NSThread currentThread]);
}
执行结果：：；
2017-12-20 13:56:45.573695+0800 DeadThread[9084:2492640] 并发2 start ：：：<NSThread: 0x604000077d80>{number = 1, name = main}
2017-12-20 13:56:45.573891+0800 DeadThread[9084:2492640] 并发2 end ：：：<NSThread: 0x604000077d80>{number = 1, name = main}
2017-12-20 13:56:45.573907+0800 DeadThread[9084:2492674] 并发2 index 0 ::: <NSThread: 0x60c000265a40>{number = 3, name = (null)}
2017-12-20 13:56:45.573908+0800 DeadThread[9084:2492675] 并发2 index 10 ::: <NSThread: 0x60400026f000>{number = 4, name = (null)}
2017-12-20 13:56:45.574283+0800 DeadThread[9084:2492674] 并发2 index 1 ::: <NSThread: 0x60c000265a40>{number = 3, name = (null)}
2017-12-20 13:56:45.574344+0800 DeadThread[9084:2492675] 并发2 index 11 ::: <NSThread: 0x60400026f000>{number = 4, name = (null)}
2017-12-20 13:56:45.574420+0800 DeadThread[9084:2492675] 并发2 index 12 ::: <NSThread: 0x60400026f000>{number = 4, name = (null)}
2017-12-20 13:56:45.574422+0800 DeadThread[9084:2492674] 并发2 index 2 ::: <NSThread: 0x60c000265a40>{number = 3, name = (null)}
得到结果：：：
1.添加两个 任务代码块，开启两个线程；
2.子线程中代码 不是按顺序执行
2.3 全局主队列：：：：
2.3.1 主队列 同步 死锁
- (void)syncMain {
NSLog(@"\n\n**************主队列同步，放到主线程会死锁***************\n\n");
// 主队列
dispatch_queue_t queue = dispatch_get_main_queue();
dispatch_sync(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"主队列同步1 %@",[NSThread currentThread]);
}
});
dispatch_sync(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"主队列同步2 %@",[NSThread currentThread]);
}
});
dispatch_sync(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"主队列同步3 %@",[NSThread currentThread]);
}
});
}
死锁原因：：：
如果在主线程中运用主队列同步，也就是把任务放到了主线程的队列中。
而同步对于任务是立刻执行的，那么当把第一个任务放进主队列时，它就会立马执行。
可是主线程现在正在处理syncMain方法，任务需要等syncMain执行完才能执行。
syncMain执行到第一个任务的时候，又要等第一个任务执行完才能往下执行第二个和第三个任务。
这样syncMain方法和第一个任务就开始了互相等待，形成了死锁。
2.3.2 主队列 异步
- (void)asyncMain {
NSLog(@"**************主队列异步***************");
// 主队列
dispatch_queue_t queue = dispatch_get_main_queue();
dispatch_async(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"主队列异步1 %@",[NSThread currentThread]);
}
});
dispatch_async(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"主队列异步2 %@",[NSThread currentThread]);
}
});
dispatch_async(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"主队列异步3 %@",[NSThread currentThread]);
}
});
}
执行结果：：：
2017-12-20 14:20:01.729412+0800 DeadThread[9257:2636939] **************主队列异步***************
2017-12-20 14:20:01.732208+0800 DeadThread[9257:2636939] 主队列异步1 <NSThread: 0x604000261080>{number = 1, name = main}
2017-12-20 14:20:01.732326+0800 DeadThread[9257:2636939] 主队列异步1 <NSThread: 0x604000261080>{number = 1, name = main}
2017-12-20 14:20:01.732456+0800 DeadThread[9257:2636939] 主队列异步1 <NSThread: 0x604000261080>{number = 1, name = main}
2017-12-20 14:20:01.732726+0800 DeadThread[9257:2636939] 主队列异步2 <NSThread: 0x604000261080>{number = 1, name = main}
2017-12-20 14:20:01.732931+0800 DeadThread[9257:2636939] 主队列异步2 <NSThread: 0x604000261080>{number = 1, name = main}
2017-12-20 14:20:01.733026+0800 DeadThread[9257:2636939] 主队列异步2 <NSThread: 0x604000261080>{number = 1, name = main}
2017-12-20 14:20:01.733128+0800 DeadThread[9257:2636939] 主队列异步3 <NSThread: 0x604000261080>{number = 1, name = main}
2017-12-20 14:20:01.733251+0800 DeadThread[9257:2636939] 主队列异步3 <NSThread: 0x604000261080>{number = 1, name = main}
2017-12-20 14:20:01.733502+0800 DeadThread[9257:2636939] 主队列异步3 <NSThread: 0x604000261080>{number = 1, name = main}
得到结果：：：
1. 主队列是个同步队列
2.4 全局并发队列
2.4.1
- (void)globalQueueOne{
NSLog(@"global1 start ：：：%@",[NSThread currentThread]);
dispatch_queue_t queue = dispatch_queue_create("test", DISPATCH_QUEUE_SERIAL);
dispatch_sync(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"global1 index %d ::: %@",i,[NSThread currentThread]);
}
});
dispatch_sync(queue, ^{
for (int i = 10; i < 13; i++) {
NSLog(@"global1 index %d ::: %@",i,[NSThread currentThread]);
}
});
NSLog(@"global1 end ：：：%@",[NSThread currentThread]);
}
执行结果：：：
2017-12-20 14:27:02.302953+0800 DeadThread[9352:2669397] global1 start ：：：<NSThread: 0x6000000655c0>{number = 1, name = main}
2017-12-20 14:27:02.303132+0800 DeadThread[9352:2669397] global1 index 0 ::: <NSThread: 0x6000000655c0>{number = 1, name = main}
2017-12-20 14:27:02.303230+0800 DeadThread[9352:2669397] global1 index 1 ::: <NSThread: 0x6000000655c0>{number = 1, name = main}
2017-12-20 14:27:02.303322+0800 DeadThread[9352:2669397] global1 index 2 ::: <NSThread: 0x6000000655c0>{number = 1, name = main}
2017-12-20 14:27:02.303397+0800 DeadThread[9352:2669397] global1 index 10 ::: <NSThread: 0x6000000655c0>{number = 1, name = main}
2017-12-20 14:27:02.303467+0800 DeadThread[9352:2669397] global1 index 11 ::: <NSThread: 0x6000000655c0>{number = 1, name = main}
2017-12-20 14:27:02.303557+0800 DeadThread[9352:2669397] global1 index 12 ::: <NSThread: 0x6000000655c0>{number = 1, name = main}
2017-12-20 14:27:02.303638+0800 DeadThread[9352:2669397] global1 end ：：：<NSThread: 0x6000000655c0>{number = 1, name = main}
2.4.2
- (void)globalQueueTwo{
NSLog(@"global2 start ：：：%@",[NSThread currentThread]);
dispatch_queue_t queue = dispatch_queue_create("test", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
for (int i = 0; i < 3; i++) {
NSLog(@"global2 index %d ::: %@",i,[NSThread currentThread]);
}
});
dispatch_async(queue, ^{
for (int i = 10; i < 13; i++) {
NSLog(@"global2 index %d ::: %@",i,[NSThread currentThread]);
}
});
NSLog(@"global2 end ：：：%@",[NSThread currentThread]);
}
执行结果：：：
2017-12-20 14:28:27.498062+0800 DeadThread[9382:2678820] global2 start ：：：<NSThread: 0x600000076700>{number = 1, name = main}
2017-12-20 14:28:27.498208+0800 DeadThread[9382:2678820] global2 end ：：：<NSThread: 0x600000076700>{number = 1, name = main}
2017-12-20 14:28:27.498250+0800 DeadThread[9382:2679707] global2 index 0 ::: <NSThread: 0x60c0000779c0>{number = 3, name = (null)}
2017-12-20 14:28:27.498260+0800 DeadThread[9382:2679706] global2 index 10 ::: <NSThread: 0x60400007e800>{number = 4, name = (null)}
2017-12-20 14:28:27.498555+0800 DeadThread[9382:2679707] global2 index 1 ::: <NSThread: 0x60c0000779c0>{number = 3, name = (null)}
2017-12-20 14:28:27.498692+0800 DeadThread[9382:2679706] global2 index 11 ::: <NSThread: 0x60400007e800>{number = 4, name = (null)}
2017-12-20 14:28:27.498710+0800 DeadThread[9382:2679707] global2 index 2 ::: <NSThread: 0x60c0000779c0>{number = 3, name = (null)}
2017-12-20 14:28:27.498753+0800 DeadThread[9382:2679706] global2 index 12 ::: <NSThread: 0x60400007e800>{number = 4, name = (null)}
