Question

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, .weekOfYear], from: self)) else { return nil }
        return gregorian.date(byAdding: .day, 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

Answer 1

这是Swift 3版本： -

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, .weekOfYear], from: self)) else { return nil }
        return gregorian.date(byAdding: .day, value: 7, to: sunday)
    }
}

您可以像这样获得周开始日期和结束日期：

let startWeek = Date().startOfWeek
let endWeek = Date().endOfWeek

print(startWeek ?? "not found start date")
print(endWeek ?? "not found end date")

Answer 2

您的代码工作正常。如果要在Playground中运行代码，则可以看到实际的Date对象而不是String表示。即使你没有指定DateFormatter，在做print(Date())时，Swift使用DateFormatter打印Date个对象，因此该值将是相对时间而不是Date对象提供的绝对时间点。

在游乐场中，您可以看到实际的startOfWeek为"Sep 25, 2017 at 12:00 AM"，而endOfWeek为"Oct 1, 2017 at 12:00 AM"，这是本周的正确值。

请勿使用print(Date())来检查Date个对象的正确性，因为正如您所看到的，由于使用了基础DateFormatter，它会产生意外结果。< / p>

如何在swift中获得本周的开始和结束？

2 个答案: