异步处理3:使用nslock锁定线程

锁定线程:确保两个线程(处理的程序)不会使用同一段代码

1.添加一个属性:@property(nonatomic,strong)NSLock*threadLock;  
2.viewDidLoad中新建对象NSLock,self.threadLock=[NSLock alloc]init];
3.在适当的位置添加锁[self.threadLock lock];
4.适当的位置: 

-(void)bigTask{
** [self.threadLock lock];**
    @autoreleasepool {

        int updateUIWhen = 500;
        for (int i=0; i<10000; i++) {
            
            NSString*newString=[NSString stringWithFormat:@"i=%d",i];
            NSLog(@"%@ ",newString);
            
            if (i==updateUIWhen) {
              
                float f=(float)i/10000;
               
                NSNumber*percentDone=[NSNumber numberWithFloat:f];
               
                [self performSelectorOnMainThread:@selector(updateProgressViewWithPercentage:)withObject:percentDone waitUntilDone:YES];
                
                updateUIWhen=updateUIWhen+1000;

            }
            
            
        }
        
        [self performSelectorOnMainThread:@selector(updateProgressViewWithPercentage:)withObject:[NSNumber numberWithFloat:1.0] waitUntilDone:YES];
        
        [self.myActivityIndicator stopAnimating];
    }
    
   ** [self.threadLock unlock];**
}

打 ** 的地方就是 加锁的地方

结果: 程序运行点击一次,会扥到for循环 也就是进度条执行完成后才会执行下一次的运行