iOS 之NSOperation（一）

一、NSOperation的介绍

1、NSOperation的作用

配合使用NSOperation和NSOperationQueue实现多线程编程

2、实现多线程的具体步骤

1）将需要执行的操作封装到一个NSOperation对象中

2）将NSOperation对象添加到NSOperationQueue中

3）系统自动将NSOperationQueue中的NSOperation取出来，并且将封装的操作放到一条新线程中执行

3、NSOperation十个抽象类，并没有封装操作的能力，必须使用它的子类

4、子类的三种形式

1）NSInvocationOperation

2）NSBlockOpera

3）自定义继承自NSOperation的子类，实现内部相应的方法

二、结合代码

1、NSInvocationOperation的使用

1）没有添加到队列

- (void)useNSInvocationOperation
{
    //1.封装操作
    NSInvocationOperation * operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationTask) object:nil];
    //开始执行
    [operation1 start];

    NSInvocationOperation * operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationTask2) object:nil];
    [operation2 start];

}
- (void)invocationTask
{
    NSLog(@"invocationTask,%@",[NSThread currentThread]);
}
- (void)invocationTask2
{
    NSLog(@"invocationTask2,%@",[NSThread currentThread]);
}

打印结果：

2016-03-14 17:53:59.638 NSoperation[3071:257804] invocationTask,<NSThread: 0x7f86fad06cb0>{number = 1, name = main}
2016-03-14 17:53:59.639 NSoperation[3071:257804] invocationTask2,<NSThread: 0x7f86fad06cb0>{number = 1, name = main}

注意事项：结果中可以看出如果没有放到队列中，默认同步执行，都在主线程。

2）添加到队列

 - (void)useNSInvocationOperation
 {
     //1.封装操作
     NSInvocationOperation * operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationTask) object:nil];

     NSInvocationOperation * operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationTask2) object:nil];

     //2.创建队列
     NSOperationQueue * queue = [[NSOperationQueue alloc]init];
     queue.maxConcurrentOperationCount = ;//最大线程数：2-3最好

     //3.添加操作到队列
     [queue addOperation:operation1];
     [queue addOperation:operation2];

 }
 - (void)invocationTask
 {
     NSLog(@"invocationTask,%@",[NSThread currentThread]);
 }
 - (void)invocationTask2
 {
     NSLog(@"invocationTask2,%@",[NSThread currentThread]);
 }

打印结果：

2016-03-14 17:57:33.192 NSoperation[3083:261277] invocationTask2,<NSThread: 0x7fd9b8f07ee0>{number = 2, name = (null)}
2016-03-14 17:57:33.192 NSoperation[3083:261278] invocationTask,<NSThread: 0x7fd9b8e13210>{number = 3, name = (null)}

根据打印结果可以看出加入队列之后，系统又开启了两条线程。

2、NSBlockOperation的使用

 //1.封装操作
     NSBlockOperation * operation1 = [NSBlockOperation blockOperationWithBlock:^{
         NSLog(@"NSBlockOperation---operation1,%@",[NSThread currentThread]);
     }];
     //2.添加更多的操作
     [operation1 addExecutionBlock:^{
         NSLog(@"NSBlockOperation---%@",[NSThread currentThread]);
     }];

     [operation1 start];

输出结果：

2016-03-14 18:04:22.577 NSoperation[3105:266124] NSBlockOperation---operation1,<NSThread: 0x7f9e7850a1c0>{number = 1, name = main}
2016-03-14 18:04:22.577 NSoperation[3105:266206] NSBlockOperation---<NSThread: 0x7f9e785a4eb0>{number = 2, name = (null)}

注意事项：只要NSBlockOperation的封装操作数大于1，就会执行一部操作

3、给线程添加依赖

 - (void)useNSInvocationOperation
 {
     //1.封装操作
     NSInvocationOperation * operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationTask) object:nil];

     NSInvocationOperation * operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationTask2) object:nil];

      NSInvocationOperation * operation3 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(invocationTask3) object:nil];

     //2.创建队列
     NSOperationQueue * queue = [[NSOperationQueue alloc]init];
     queue.maxConcurrentOperationCount = ;//最大线程数：2-3最好

     //2.1设置依赖
     [operation1 addDependency:operation3];
     [operation3 addDependency:operation2];

     //3.添加操作到队列
     [queue addOperation:operation1];
     [queue addOperation:operation2];
     [queue addOperation:operation3];

 }
 - (void)invocationTask
 {
     NSLog(@"invocationTask,%@",[NSThread currentThread]);
 }
 - (void)invocationTask2
 {
     NSLog(@"invocationTask2,%@",[NSThread currentThread]);
 }
 - (void)invocationTask3
 {
     NSLog(@"invocationTask3,%@",[NSThread currentThread]);
 }

输出结果：

2016-03-14 18:12:21.066 NSoperation[3135:272293] invocationTask2,<NSThread: 0x7f845a54e500>{number = 2, name = (null)}
2016-03-14 18:12:21.067 NSoperation[3135:272293] invocationTask3,<NSThread: 0x7f845a54e500>{number = 2, name = (null)}
2016-03-14 18:12:21.067 NSoperation[3135:272293] invocationTask,<NSThread: 0x7f845a54e500>{number = 2, name = (null)}

根据结果可以看出先执行的2又执行的3最后执行的1，并没有根据添加到队列的顺序执行。

4、设置线程的优先级

1)operation1.queuePriority = NSOperationQueuePriorityHigh;

2)优先级的取值

NSOperationQueuePriorityVeryLow = -8L,

NSOperationQueuePriorityLow = -4L,

NSOperationQueuePriorityNormal = 0,

NSOperationQueuePriorityHigh = 4,

NSOperationQueuePriorityVeryHigh = 8