NSNotificationcenter没有成员名称＆＃39; defaultCenter＆＃34;错误-Swift

Question

尝试在swift中添加键盘观察器并获取错误

NSNotificationcenter does not have a member names 'defaultCenter"

使用

NSNotificationCenter().defaultCenter().addObserver(self, selector: Selector("keyboardWillAppear"), name: UIKeyboardWillShowNotification, object: nil)
NSNotificationCenter().defaultCenter().addObserver(self, selector: Selector("keyboardWillHide"), name: UIKeyboardWillHideNotification, object: nil)

根据以下建议 NSNotificationCenter addObserver in Swift Swift: Keyboard Observer via NSNotificationCenter doesn't work

如果我删除defaultCenter我没有收到错误，但也没有观察键盘

NSNotificationCenter().addObserver(self, selector: Selector("keyboardWillAppear"), name: UIKeyboardWillShowNotification, object: nil)
NSNotificationCenter().addObserver(self, selector: Selector("keyboardWillHide"), name: UIKeyboardWillHideNotification, object: nil)

Answer 1

defaultCenter是类方法（在Swift中也称为类型方法），因此它是

NSNotificationCenter.defaultCenter()

而不是

NSNotificationCenter().defaultCenter()

会在对象上调用实例方法 defaultCenter() 由NSNotificationCenter()创建并返回。