swift--使用URLSession异步加载图片

 self.imageV.frame = CGRect(x:20,y:70,width:kScreenWidth-40,height:200)
        self.view.addSubview(self.imageV)
        
        //使用URLSession加载图片
        let url = URL(string:"http://pic.jj20.com/up/allimg/911/021616153629/160216153629-1.jpg")
        //创建请求对象
        let request = URLRequest(url:url!)
        
        let session = URLSession.shared
        let dataTask = session.dataTask(with: request,completionHandler: {
            (data, response, error) -> Void in
            if error != nil{
                print(error.debugDescription)
            }else{
                //将图片数据赋予UIImage
                let img = UIImage(data:data!)
                self.imageV.image = img
            }
        }) as URLSessionTask
        
        //启动任务
        dataTask.resume()