NSOperation小结

·NSOperation简介:
1.简单说明
NSOperation的作⽤：配合使用NSOperation和NSOperationQueue也能实现多线程编程
NSOperation和NSOperationQueue实现多线程的具体步骤：
（1）先将需要执行的操作封装到一个NSOperation对象中
（2）然后将NSOperation对象添加到NSOperationQueue中
（3）系统会⾃动将NSOperationQueue中的NSOperation取出来
（4）将取出的NSOperation封装的操作放到⼀条新线程中执⾏

2.NSOperation的子类
NSOperation是个抽象类,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）NSInvocationOperation
（2）NSBlockOperation
（3）自定义子类继承NSOperation,实现内部相应的⽅法

代码：

   1.
   //直接start ，是在主线程执行，放在队列中，就在队列的线程中执行
    NSBlockOperation * operation1 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"thread1==%@",[NSThread currentThread]);
    }];
    [operation1 start];
控制台输出：
2016-12-20 16:54:22.261 NSOperation[30410:19443376] thread1=={number = 1, name = main}
注：number=1才是主线程，number是线程的ID

    2.
    NSOperationQueue * queue = [[NSOperationQueue alloc]init];
    NSBlockOperation * operation1 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"thread1==%@",[NSThread currentThread]);
    }];
    [queue addOperation:operation1];
控制台输出:
2016-12-20 16:55:39.997 NSOperation[30439:19445283] thread1=={number = 3, name = (null)}

   3.
   NSOperationQueue * queue = [NSOperationQueue mainQueue];
   //直接start ，是在主线程执行，放在队列中，就在队列的线程中执行
   NSBlockOperation * operation1 = [NSBlockOperation blockOperationWithBlock:^{
       NSLog(@"thread1==%@",[NSThread currentThread]);
   }];
   [queue addOperation:operation1];
控制台输出:
2016-12-20 16:56:36.720 NSOperation[30459:19446751] thread1=={number = 1, name = main}```

4 添加依赖
NSOperationQueue * queue = [[NSOperationQueue alloc]init];
//直接start ，是在主线程执行，放在队列中，就在队列的线程中执行
NSBlockOperation * operation1 = [NSBlockOperation blockOperationWithBlock:^{
    sleep(5);
    NSLog(@"thread1==%@",[NSThread currentThread]);
    sleep(2);
}];

NSBlockOperation * operation2 = [NSBlockOperation blockOperationWithBlock:^{
    sleep(2);
    NSLog(@"thread2==%@",[NSThread currentThread]);
}];

NSBlockOperation * blockOp = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"1111111111111");
}];
//添加依赖，前面的依赖后面的,在后面的执行完再执行前面的
//blockOp 依赖operation1 和 operation2，在他们执行完之后再执行blockOp
[blockOp addDependency:operation1];
[blockOp addDependency:operation2];

[queue addOperation:operation1];
[queue addOperation:operation2];
[queue addOperation:blockOp];
NSLog(@"123433434");

控制台输出:
2016-12-20 17:01:22.929 NSOperation[30530:19451239] 123433434
2016-12-20 17:01:25.003 NSOperation[30530:19451358] thread2=={number = 3, name = (null)}
2016-12-20 17:01:28.003 NSOperation[30530:19451359] thread1=={number = 4, name = (null)}
2016-12-20 17:01:30.079 NSOperation[30530:19451358] 1111111111111

5.注意，在任务里再次开分线程，执行异步方法，添加依赖之后，没有用，同步方法才有用
NSBlockOperation * operation1 = [NSBlockOperation blockOperationWithBlock:^{
//异步方法
dispatch_async(dispatch_get_global_queue(0, 0), ^{
sleep(5);
NSLog(@"thread1==%@",[NSThread currentThread]);
sleep(2);
});
}];

NSBlockOperation * operation2 = [NSBlockOperation blockOperationWithBlock:^{
    sleep(2);
    NSLog(@"thread2==%@",[NSThread currentThread]);
}];

NSBlockOperation * blockOp = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"1111111111111");
}];
[blockOp addDependency:operation1];
[blockOp addDependency:operation2];

[queue addOperation:operation1];
[queue addOperation:operation2];
[queue addOperation:blockOp];
NSLog(@"123433434");

控制台输出:
2016-12-20 17:06:50.847 NSOperation[30601:19455477] 123433434
2016-12-20 17:06:52.919 NSOperation[30601:19455612] thread2=={number = 3, name = (null)}
2016-12-20 17:06:52.919 NSOperation[30601:19455612] 1111111111111
2016-12-20 17:06:55.922 NSOperation[30601:19455633] thread1=={number = 4, name = (null)}

6.添加循环依赖也是没用的，例如a依赖b，b依赖c，c依赖a,互相依赖队列是不会执行的

谢谢大家，感谢胡同学 =。=