本篇文章主要介绍下多线程下NSOperation、NSBlockOperation、NSInvocationOperation、NSOperationQueue的使用，列举几个简单的例子。
默认情况下，NSOperation并不具备封装操作的能力，必须使用它的子类，使用NSOperation子类的方式有3种：
1> 自定义子类继承NSOperation，实现内部相应的方法
2> NSBlockOperation
3>NSInvocationOperation
这讲先介绍如何用NSOperation封装一个操作，后面再结合NSOperationQueue来使用。
1.首先介绍自定义NSOperation：
NSOperation是没法直接使用的，它只是提供了一个工作的基本逻辑，具体实现还是需要你通过定义自己的NSOperation子类来获得。
[objc] view plain copy #import <Foundation/Foundation.h> @protocol NSDefineOprationDelegate <NSObject> - (void) handleDelegate; @end @interface NSDefineOpration : NSOperation @property (nonatomic, assign) id <NSDefineOprationDelegate> delegate; - (id)initWithDelegate:(id<NSDefineOprationDelegate>) delegate; @end
实现文件里：
[objc] view plain copy #import "NSDefineOpration.h" @implementation NSDefineOpration - (id)initWithDelegate:(id<NSDefineOprationDelegate>) delegate { if(self = [super init]) { self.delegate = delegate; } return self; } - (void)main { @autoreleasepool { //do something sleep(15); NSLog(@"op1........handle...... on thread num :%@",[NSThread currentThread]); if([self.delegate respondsToSelector:@selector(handleDelegate)]) { [self.delegate performSelector:@selector(handleDelegate) withObject:nil]; } } } @end
这里的sleep（15）主要用来做一些延时的操作，比如网络下载等。调用：
[objc] view plain copy - (void)oprationTest { NSDefineOpration *op1 = [[NSDefineOpration alloc] initWithDelegate:self]; op1.completionBlock = ^(){ NSLog(@"op1........OK !!"); }; [op1 start]; }
执行结果：
[objc] view plain copy 2014-03-22 16:49:44.367 Operation[17353:60b] op1........handle...... on thread num :<NSThread: 0x1654ea20>{name = (null), num = 1} 2014-03-22 16:49:49.373 Operation[17353:60b] op1.....callback..... on thread num :<NSThread: 0x1654ea20>{name = (null), num = 1} 2014-03-22 16:49:49.377 Operation[17353:1807] op1........OK !!
从执行结果可以看出，因为在实现的main函数里没有使用异步线程处理，导致直接阻塞了主线程1，所以使用这种方式一定注意main函数里操作时间过长导致主线程阻塞问题。耗时比较长的都放到其他线程里处理。
2.接下来介绍NSBlockOperation
第一种使用NSBlockOperation的方式：
[objc] view plain copy NSLog(@"block start"); NSBlockOperation *bop2 = [NSBlockOperation blockOperationWithBlock:^{ sleep(15); NSLog(@"bop2.....handle..... on thread num%@",[NSThread currentThread]); }]; [bop2 setCompletionBlock:^{ NSLog(@"bop2........OK !!"); }]; [bop2 start];
* 第2行初始化了一个NSBlockOperation对象，它是用一个Block来封装需要执行的操作
* 第9行调用了start方法，紧接着会马上执行Block中的内容
看下执行结果：
[objc] view plain copy 2014-03-22 16:57:51.903 Operation[17374:60b] block start 2014-03-22 16:58:06.908 Operation[17374:60b] bop2.....handle..... on thread num<NSThread: 0x16d83910>{name = (null), num = 1} 2014-03-22 16:58:06.912 Operation[17374:360b] bop2........OK !!
* 这里还是在当前线程同步执行操作，并没有异步执行，阻塞主线程。
第二种使用NSBlockOperation的方式：
[objc] view plain copy - (void)blockOprationTest { NSLog(@"block start"); NSBlockOperation * op2 = [[NSBlockOperation alloc] init]; [op2 addExecutionBlock:^{ sleep(10); NSLog(@"op2.....handle..... on 10 hread num%@",[NSThread currentThread]); }]; [op2 addExecutionBlock:^{ sleep(6); NSLog(@"op2.....handle..... on 6 thread num%@",[NSThread currentThread]); }]; [op2 addExecutionBlock:^{ sleep(4); NSLog(@"op2.....handle..... on 4 thread num%@",[NSThread currentThread]); }]; [op2 addExecutionBlock:^{ sleep(8); NSLog(@"op2.....handle..... on 8 thread num%@",[NSThread currentThread]); }]; [op2 addExecutionBlock:^{ sleep(1); NSLog(@"op2.....handle..... on 1 thread num%@",[NSThread currentThread]); }]; [op2 setCompletionBlock:^{ NSLog(@"op2........OK !!"); }]; [op2 start]; //bop2 NSBlockOperation *bop2 = [NSBlockOperation blockOperationWithBlock:^{ sleep(15); NSLog(@"bop2.....handle..... on thread num%@",[NSThread currentThread]); }]; [bop2 setCompletionBlock:^{ NSLog(@"bop2........OK !!"); }]; [bop2 start]; }
执行结果：
[objc] view plain copy 2014-03-22 17:02:56.027 Operation[17396:60b] block start 2014-03-22 17:03:02.032 Operation[17396:1803] op2.....handle..... on 6 thread num<NSThread: 0x17573400>{name = (null), num = 2} 2014-03-22 17:03:06.032 Operation[17396:60b] op2.....handle..... on 10 hread num<NSThread: 0x1755eca0>{name = (null), num = 1} 2014-03-22 17:03:06.035 Operation[17396:1803] op2.....handle..... on 4 thread num<NSThread: 0x17573400>{name = (null), num = 2} 2014-03-22 17:03:07.038 Operation[17396:1803] op2.....handle..... on 1 thread num<NSThread: 0x17573400>{name = (null), num = 2} 2014-03-22 17:03:14.035 Operation[17396:60b] op2.....handle..... on 8 thread num<NSThread: 0x1755eca0>{name = (null), num = 1} 2014-03-22 17:03:14.037 Operation[17396:1807] op2........OK !! 2014-03-22 17:03:29.038 Operation[17396:60b] bop2.....handle..... on thread num<NSThread: 0x1755eca0>{name = (null), num = 1} 2014-03-22 17:03:29.041 Operation[17396:180b] bop2........OK !!
分析下结果：
首先看到了有1和2两个线程，线程2在56秒的时候开始执行6秒的操作，接下来执行4，1秒结束时间为07秒。线程1在56的时候开始执行10秒的操作，接下来执行8秒，结束时间为14秒。最后执行Bop2的15秒操作至29秒。时间看起来没有问题。为什么会启用2个线程而不是3个或者更多？
3.接下来介绍NSInvocationOperation
[objc] view plain copy - (void)invocationOperation { NSInvocationOperation * op3 = [[NSInvocationOperation alloc] initWithTarget:(id)self selector:@selector(handleInvoOpDelegate) object:nil]; [op3 setCompletionBlock:^{ NSLog(@"op3........OK !!"); }]; [op3 start]; }
selector函数：
[objc] view plain copy - (void)handleInvoOpD { sleep(5); NSLog(@"op3.....handle..... on thread num :%@",[NSThread currentThread]); }
执行结果：
[objc] view plain copy 2014-03-22 17:11:13.050 Operation[17421:60b] op3.....handle..... on thread num :<NSThread: 0x1653ac30>{name = (null), num = 1} 2014-03-22 17:11:13.055 Operation[17421:1803] op3........OK !!
NSInvocationOperation比较简单，就是继承了NSOperation，区别就是它是基于一个对象和selector来创建操作，可以直接使用而不需继承来实现自己的操作处理。
4.最后介绍下NSOperationQueue
把NSOperation子类的对象放入NSOperationQueue队列中，该队列就会启动并开始处理它。队列里可以加入很多个NSOperation, 可以把NSOperationQueue看作一个线程池，可往线程池中添加操作（NSOperation）到队列中。线程池中的线程可看作消费者，从队列中取走操作，并执行它。
实现demo：
[objc] view plain copy - (void)handleOpqueue { NSOperationQueue *qu = [[NSOperationQueue alloc] init]; NSBlockOperation * bkOp1 = [NSBlockOperation blockOperationWithBlock:^{ sleep(10); NSLog(@"bkOp1.....handle.....on thread num%@",[NSThread currentThread]); }]; [bkOp1 setCompletionBlock:^{ NSLog(@"bkOp1........OK !!"); }]; NSBlockOperation * bkOp2 = [NSBlockOperation blockOperationWithBlock:^{ sleep(2); NSLog(@"bkOp2.....handle.....on thread num%@",[NSThread currentThread]); }]; [bkOp2 setCompletionBlock:^{ NSLog(@"bkOp2........OK !!"); }]; NSBlockOperation * bkOp3 = [NSBlockOperation blockOperationWithBlock:^{ sleep(1); NSLog(@"bkOp3.....handle.....on thread num%@",[NSThread currentThread]); }]; [bkOp3 setCompletionBlock:^{ NSLog(@"bkOp3........OK !!"); }]; NSBlockOperation * bkOp4 = [NSBlockOperation blockOperationWithBlock:^{ sleep(10); NSLog(@"bkOp4.....handle.....on thread num%@",[NSThread currentThread]); }]; [bkOp4 setCompletionBlock:^{ NSLog(@"bkOp4........OK !!"); }]; NSBlockOperation * bkOp5 = [NSBlockOperation blockOperationWithBlock:^{ sleep(5); NSLog(@"bkOp5.....handle.....on thread num%@",[NSThread currentThread]); }]; [bkOp5 setQueuePriority:NSOperationQueuePriorityHigh]; [bkOp5 setCompletionBlock:^{ NSLog(@"bkOp5........OK !!"); }]; NSInvocationOperation *invoOp6 = [[NSInvocationOperation alloc] initWithTarget:(id)self selector:@selector(handleInvoOp) object:nil]; [invoOp6 setCompletionBlock:^{ NSLog(@"invoOp6........OK !!"); }]; [invoOp6 setQueuePriority:NSOperationQueuePriorityHigh]; [qu setMaxConcurrentOperationCount:2]; [qu addOperation:bkOp3]; [qu addOperation:bkOp2]; [qu addOperation:bkOp1]; [qu addOperation:bkOp4]; [qu addOperation:bkOp5]; [qu addOperation:invoOp6]; }
先看下执行结果：
[objc] view plain copy 2014-03-22 17:18:36.634 Operation[17439:1803] bkOp3.....handle.....on thread num<NSThread: 0x1754c450>{name = (null), num = 2} 2014-03-22 17:18:36.638 Operation[17439:1803] bkOp3........OK !! 2014-03-22 17:18:37.635 Operation[17439:3607] bkOp2.....handle.....on thread num<NSThread: 0x1765a320>{name = (null), num = 3} 2014-03-22 17:18:37.637 Operation[17439:3607] bkOp2........OK !! 2014-03-22 17:18:41.640 Operation[17439:3d07] bkOp5.....handle.....on thread num<NSThread: 0x17562d10>{name = (null), num = 4} 2014-03-22 17:18:41.642 Operation[17439:3d07] bkOp5........OK !! 2014-03-22 17:18:42.639 Operation[17439:1803] invoOp6.....handle..... on thread num :<NSThread: 0x1754c450>{name = (null), num = 2} 2014-03-22 17:18:42.643 Operation[17439:1803] invoOp6........OK !! 2014-03-22 17:18:51.644 Operation[17439:3607] bkOp1.....handle.....on thread num<NSThread: 0x1765a320>{name = (null), num = 3} 2014-03-22 17:18:51.646 Operation[17439:3607] bkOp1........OK !! 2014-03-22 17:18:52.645 Operation[17439:3d07] bkOp4.....handle.....on thread num<NSThread: 0x17562d10>{name = (null), num = 4} 2014-03-22 17:18:52.647 Operation[17439:3d07] bkOp4........OK !!
从结果可以看出，NSOperationQueue在2，3，4这3个线程里去处理NSOperation，而不包括主线程1。此外，在设置了bkop5以及invOp6的优先级为高时，他们会优先执行，当然这个优先时相对，是相对正在排队的，不包括已经正在执行的。
总结：NSOperation、NSBlockOperation、NSInvocationOperation、NSOperationQueue都比较简单，NSOperation、NSBlockOperation、NSInvocationOperation单个都是表示一种操作，而NSOperationQueue是一个可以包含多个NSOperation的队列，可以自己在多个线程处理，只要加入队列之后，我们就不用去操作，直到Callback或者完成。
参考资料：
http://blog.csdn.net/totogo2010/article/details/8013316
http://www.cnblogs.com/mjios/archive/2013/04/19/3029765.html
转载于:https://www.cnblogs.com/piaojin/p/5591661.html
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