Swift | 优雅的通知

寻求优雅之道，最便捷的方式就是细品苹果的代码。

比如键盘显示隐藏的通知，苹果是这样写的：

extension UIResponder {

    public class let keyboardWillShowNotification: NSNotification.Name

    public class let keyboardDidShowNotification: NSNotification.Name

    public class let keyboardWillHideNotification: NSNotification.Name

    public class let keyboardDidHideNotification: NSNotification.Name

}

接收通知：

NotificationCenter.default.addObserver(self, selector: #selector(handleNotif), name: UIResponder.keyboardWillShowNotification, object: nil)

苹果的这种写法非常清晰规范，我们可以仿照其写法，比如用户登录成功的通知：

extension User {
    /// 用户登录成功的通知
    static let userDidLogInNotification = Notification.Name(rawValue: "User.userDidLogInNotification")
}

其实之前苹果的通知不是这种格式，而是：

extension NSNotification.Name {
    
    public static let UIKeyboardWillShow: NSNotification.Name
    
    public static let UIKeyboardDidShow: NSNotification.Name
    
    public static let UIKeyboardWillHide: NSNotification.Name
    
    public static let UIKeyboardDidHide: NSNotification.Name
    
}

我猜想苹果之所以换了种写法，有可能是考虑到代码的组织，同样是键盘显示隐藏通知，对NSNotification.Name进行扩展和对UIResponder进行扩展，我觉得后者的内聚度更高。

苹果已经给我们提供了最优雅的模板，以后我们依葫芦画瓢就可以了。

参考：

• https://developer.apple.com/documentation/foundation/nsnotification/name
• https://stackoverflow.com/questions/41648539/how-can-i-get-the-keyboards-height