如何在swift中获得本周的开始和结束？

参见英文答案 > How do I find the beginning of the week from an NSDate?????????????????????????????????????4个
>???????????? How to get Monday’s date of the current week in swift????????????????????????????????????7个
如何在swift中获得本周的开始和结束？
这是我的代码

extension Date {
    var startOfWeek: Date? {
        let gregorian = Calendar(identifier: .gregorian)
        guard let sunday = gregorian.date(from: gregorian.dateComponents([.yearForWeekOfYear,.weekOfYear],from: self)) else { return nil }
        return gregorian.date(byAdding: .day,value: 1,to: sunday)
    }

    var endOfWeek: Date? {
        let gregorian = Calendar(identifier: .gregorian)
        guard let sunday = gregorian.date(from: gregorian.dateComponents([.yearForWeekOfYear,value: 7,to: sunday)
    }
}

我这样打电话

let startWeek = Date().startOfWeek
let endWeek = Date().endOfWeek
print(startWeek!)
print(endWeek!)
var dateFormat1 = DateFormatter()
dateFormat1.dateFormat = "dd-MM-yy"
let startWeek2 = dateFormat1.string(from: startWeek!)
var dateFormat12 = DateFormatter()
dateFormat12.dateFormat = "dd-MM-yy"
let endWeek2 = dateFormat12.string(from: endWeek!)
print(startWeek2)
print(endWeek2)

和输出

2017-09-24 18:30:00 +0000
2017-09-30 18:30:00 +0000
25-09-17
01-10-17