//避免循环引用，weak当对象销毁的时候，对象会被指定为nil
        //weak var weakSelf = self //对象推到，省略了ViewController
        weak var weakSelf : FirstViewController? = self  //等同与上面的表达式
        
        ljload?.loadData({ (jsonData:String) in
            print("获取到的数据:\(jsonData)")
            
            weakSelf?.view.backgroundColor = UIColor.red
        })