使用NSOperationQueue实现异步处理

@implementation ViewController
{
    NSOperationQueue*mainQueue;
    NSOperationQueue*serialQueue;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    mainQueue=[NSOperationQueue mainQueue];
    serialQueue=[[NSOperationQueue alloc]init];
    serialQueue.maxConcurrentOperationCount=1;

...

-(void)bigTaskAction{



   [serialQueue addOperationWithBlock: ^{
      
       [mainQueue addOperationWithBlock: ^{
            
            [self.myActivityIndicator startAnimating];
       
        }];
        
        int updateUIWhen=1000;
       
        for (int i=0;i<10000;i++) {
            NSString*newString=[NSString stringWithFormat:@"i=%i",i ];
            NSLog(@"%@ ",newString);
            if (i==updateUIWhen) {
                float f =(float)i/10000;
                NSNumber*percentDone=[NSNumber numberWithFloat:f];

               [mainQueue addOperationWithBlock: ^{
                    
                    [self.myProcessView setProgress:[percentDone floatValue ]animated:YES];
                    
                }];
                updateUIWhen=updateUIWhen+500;
            }
        }
      [mainQueue addOperationWithBlock:^{
            
            [self.myProcessView setProgress:1.0 animated:YES];

            [self.myActivityIndicator stopAnimating];
        }];
    }];
    
}