swift - 以更快速的方式从 Any Object 确定 Swift 对象类型

Question

我有一个 [String:Any] 的字典，当我从 UserDefaults 加载时，我得到了一个 Date 对象，但是来自 Firebase我取回了一个 Timestamp 对象。

肯定有我的 Swifty 方式来编写这段代码吗？

var correctDate:Date!

if let t = dictionary[key.timestamp] as? Timestamp {
    print("as Timestamp")
    correctDate = t.dateValue()
}
else if let t = dictionary[key.timestamp] as? Date {
    print("as Date")
    correctDate = t
}
else {
    fatalError("no date object found")
}

print(correctDate)

Answer 1

switch 是否更 Swifty？:

switch dictionary[key.timestamp] {
case let timestamp as Timestamp:
    print("as TimeStamp")
    correctDate = timestamp.dateValue()
case let date as Date:
    print("as Date")
    correctDate = date
default:
    fatalError("no date object found")
}

---

使用协议(protocol)

您有两个对象，它们都代表日期对象。为什么不用协议(protocol)统一它们并给它们一个通用接口(interface)？

使用协议(protocol)创建 Date 和 Timestamp 都采用的 DateObject:

protocol DateObject {
    var date: Date { get }
}

extension Date: DateObject {
    var date: Date { return self }
}

extension Timestamp: DateObject {
    var date: Date { return self.dateValue() }
}

// Added this extension for NSDate after comments
// indicated that NSDate objects were coming back
// from UserDefaults
extension NSDate: DateObject {
    var date: Date { return self as Date }
}

if let date = (dictionary[key.timestamp] as? DateObject)?.date {
    print("has date")
    correctDate = date
} else {
    fatalError("no date object found")
}