Failable Initializer的init（fileURL :)不能覆盖不可用的初始化程序

Question

我不确定如何在Xcode 6.4中修复此错误

override init?(fileURL url: NSURL) {
    super.init(fileURL: url)

    let center = NSNotificationCenter.defaultCenter()
    center.addObserver(self, selector: "thingsDidChange:", name: WhatsitDidChangeNotification, object: nil)
}

deinit {
    let center = NSNotificationCenter.defaultCenter()
    center.removeObserver(self)
}

Answer 1

init?(_:)函数中没有任何内容可能会失败并迫使您返回nil。只需删除init签名的尾随问号。

override init(fileURL url: NSURL) {
    super.init(fileURL: url)
    let center = NSNotificationCenter.defaultCenter()
    center.addObserver(self, selector: "thingsDidChange:", name: WhatsitDidChangeNotification, object: nil)
}