NSOperation介绍

NSOperation

简介

NSOperation 是基于GCD的一个抽象基类 ，将线程封装成要执行的操作，不需要管理线程的生命周期和同步，但比GCD可空性更强，例如可以加入操作依赖（addDependency）控制操作执行顺序，设置操作队列最大可并发执行的操作个数（setMaxConcurrentOperationCount),取消操作（cancel）等。

NSOperation作为抽象基类不具备封装开发者的操作的功能，需要使用两个它的实体子类：NSBlockOperarion和NSInvocationOperation,或者继承NSOperation自定义子类。

后者执行代码块，相对来说后者h更加灵活易用。NSOperation操作配置完成后便可调用start 函数在当前线程执行，如果要异步执行避免阻塞当前线程，那么可以加入 NSOperationQueue中异步执行。

简单使用

NSInvocationOperation

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

[invoOpertion start];

NSBlockOperation

NSBlockOperation * blkOperation = [NSBlockOperation blockOperationWithBlock:^{
         
 }];
 
 [blkOperation start];

NSBlockOperation可以追加方法 并行执行代码块

  //线程并发队列
    NSBlockOperation * blkOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"blkOperation1==%@",[NSThread currentThread]);
    }];
    
    [blkOperation addExecutionBlock:^{
        NSLog(@"blkOperation2==%@",[NSThread currentThread]);

    }];
    
    [blkOperation addExecutionBlock:^{
        NSLog(@"blkOperation3==%@",[NSThread currentThread]);

    }];
    
    [blkOperation addExecutionBlock:^{
        NSLog(@"blkOperation4==%@",[NSThread currentThread]);

    }];

打印

2019-12-09 12:51:42.347499+0800 NSOperation[18718:3909369] blkOperation1==<NSThread: 0x28370a600>{number = 1, name = main}
2019-12-09 12:51:42.347517+0800 NSOperation[18718:3909551] blkOperation2==<NSThread: 0x283754480>{number = 5, name = (null)}
2019-12-09 12:51:42.347611+0800 NSOperation[18718:3909548] blkOperation4==<NSThread: 0x283774400>{number = 6, name = (null)}
2019-12-09 12:51:42.347611+0800 NSOperation[18718:3909549] blkOperation3==<NSThread: 0x283768c80>{number = 4, name = (null)}

NSOperation 实现同步 及设置线程依赖

//    //获取主队列
    NSOperationQueue * queue = [NSOperationQueue mainQueue];
    
    NSOperation* c = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"c");
    }];
    
    NSOperation * a = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"a");
    }];
   
    
    NSOperation * b = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"b");
    }];
    
   
    ///添加依赖 c依赖于a和b，这样c一定会在a和b完成之后才会执行
    
    [c addDependency:a];
    
    [c addDependency:b];
    
    ///添加到队列 （添加顺序故意不安顺序）
    [queue addOperation:c];
    [queue addOperation:a];
    [queue addOperation:b];

打印 可以设置各种操作之间的依赖实现线程同步

2019-12-09 13:20:53.192859+0800 NSOperation[18782:3923375] a
2019-12-09 13:20:53.194242+0800 NSOperation[18782:3923375] b
2019-12-09 13:20:53.200412+0800 NSOperation[18782:3923375] c