ios - swift/ Spring 'Date components' 错误

Question

这是接收问题代码的代码行:

let components: NSDateComponents = calendar.components(unitFlags, fromDate: earliest, toDate: latest, options: [])

问题代码:

'components' produces 'Date Components', not the expected contextual result type 'NSDateComponents'

附加代码:

public func timeAgoSinceDate(date:NSDate, numericDates:Bool) -> String {
let calendar = NSCalendar.current
let unitFlags: NSCalendar.Unit = [NSCalendar.Unit.minute, NSCalendar.Unit.hour, NSCalendar.Unit.day, NSCalendar.Unit.weekOfYear, NSCalendar.Unit.month, NSCalendar.Unit.year, NSCalendar.Unit.second]
let now = NSDate()
let earliest = now.earlierDate(date as Date)
let latest = (earliest == now as Date) ? date : now
let components: NSDateComponents = calendar.components(unitFlags, fromDate: earliest, toDate: latest, options: [])

Answer 1

Swift 3 为现有的值类型引入了一堆新的基础类类型，例如 Date对于 NSDate , Calendar为了 NSCalendar .一些原因是

• 提供适当的值语义，
• let和 var而不是可变和不可变的变体，
• 更多“Swifty”API。

详情可见

• SE-0069 Mutability and Foundation Value Types

您可以在值类型和相应的 NS 之间建立桥梁类型(就像您对 date as Date 所做的那样)，并且当现有的 Foundation API 是导入到 Swift 中，类型会自动桥接。

因此NSCalendar.current返回 Calendar代替 NSCalendar , 和 calendar.components返回 DateComponents而不是 NSDateComponents .

有时 Xcode 迁移器可以为您解决这些问题。如果不，您必须查找新类型及其方法。

在您的情况下，Swift 3 端口将如下所示:

func timeAgoSinceDate(date: Date, numericDates: Bool) -> String {
    let calendar = Calendar.current
    let components: Set<Calendar.Component> = [.minute, .hour, .day, .weekOfYear, .month, .year, .second]
    let now = Date()
    let (earliest, latest) = (now <= date) ? (now, date) : (date, now)
    let dateComponents = calendar.dateComponents(components, from: earliest, to: latest)

    // ...
}

请注意 Date是Comparable , 因此您可以比较日期直接如now <= date .这对于 NSDate 是不可能的(除非您明确实现)。