如何在Swift 3中使用enumerateDate查找过去50年的所有星期日？

以下代码将打印从最近的星期日开始的星期日的最后50年.

let cal = Calendar.current
// Get the date of 50 years ago today
let stopDate = cal.date(byAdding: .year, value: -50, to: Date())!

// We want to find dates that match on Sundays at midnight local time
var comps = DateComponents()
comps.weekday = 1 // Sunday

// Enumerate all of the dates
cal.enumerateDates(startingAfter: Date(), matching: comps, matchingPolicy: .previousTimePreservingSmallerComponents, repeatedTimePolicy: .first, direction: .backward) { (date, match, stop) in
    if let date = date {
        if date < stopDate {
            stop = true // We've reached the end, exit the loop
        } else {
            print("\(date)") // do what you need with the date
        }
    }
}