swift_学习中遇到的错误

（1）在VisitorView.swift文件中，懒加载一个按钮：

private var loginButton:UIButton={

let btn=UIButton()

btn.setTitle("注册", forState: UIControlState.Normal)

btn.setBackgroundImage(UIImage(named: "common_button_white_disable"), forState: UIControlState.Normal)

btn.setTitleColor(UIColor.orangeColor(), forState: UIControlState.Normal)

// 注册监听

btn.addTarget(self, action: "registerBtnClick", forControlEvents: UIControlEvents.TouchUpInside)

return btn

}()

运行报错：

Cannot convert value of type ‘NSObject -> () -> VisitorView‘ to expected argument type ‘AnyObject?‘

报错图片：

找了半天，终于发现是忘记加关键字"lazy",改为

private lazy var loginButton:UIButton

(2)