总结:同步(无论是串行还是并行)----不又一次开辟子线程

异步(无论是串行还是并行)----开辟子线程

GCD：

dispatch queue

主线程的main queue

并行队列 global dispatch queue

串行队列serial queues
一般用于按顺序同步訪问

#pragma mark - 载入多线程

- (void) _loadMutil

{

//GCD基于C语言

//1.主对列:(串行队列)

dispatch_queue_t mainQueue=dispatch_get_main_queue();

//2.全局并行队列

);

//3.创建串行队列

dispatch_queue_t queueSerial=dispatch_queue_create("jrqueue1",DISPATCH_QUEUE_SERIAL);

//4.创建并行队列

dispatch_queue_t queueConcu=dispatch_queue_create("jrqueue2",DISPATCH_QUEUE_CONCURRENT);

//同步运行+串行队列

/*

dispatch_sync(queueSerial, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"同步串行队列1-----%@",[NSThread currentThread]);

});

dispatch_sync(queueSerial, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"同步串行队列2-----%@",[NSThread currentThread]);

});

*/

//同步运行+并行队列

/*

dispatch_sync(queueConcu, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"同步并行队列1-----%@",[NSThread currentThread]);

});

dispatch_sync(queueConcu, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"同步并行队列2-----%@",[NSThread currentThread]);

});

*/

//异步运行+串行队列-----开启一个子线程，且顺序运行

/*

dispatch_async(queueSerial, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"异步串行队列1-----%@",[NSThread currentThread]);

});

dispatch_async(queueSerial, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"异步串行队列2-----%@",[NSThread currentThread]);

});

dispatch_async(queueSerial, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"异步串行队列3-----%@",[NSThread currentThread]);

});

*/

//异步运行+并行队列----开启多个线程，且并发运行(无序)

/*

dispatch_async(queueConcu, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"异步并行队列1-----%@",[NSThread currentThread]);

});

dispatch_async(queueConcu, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"异步并行队列2-----%@",[NSThread currentThread]);

});

dispatch_async(queueConcu, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"异步并行队列3-----%@",[NSThread currentThread]);

});

*/

//主对列+同步运行-----死锁（将下面两个加入到主队列，等待前面的运行完毕（loadView。

loadData之类的），可是当运行到这一步时，形成死循环）

/*

dispatch_sync(mainQueue, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"同步主队列1-----%@",[NSThread currentThread]);

});

dispatch_sync(mainQueue, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"同步主队列2-----%@",[NSThread currentThread]);

});

*/

}

@end

将以上的方法，在viewDidLoad 中调用一下。看看效果怎样~