斯威夫特 - 打印今年当前的一周

Question

今年到目前为止，我需要一种打印周数的方法。 我已设法打印天数和月数（请参阅下面的代码）。 但无法弄清楚如何在总周数内做同样的事情。

今年到目前为止的总天数：

let dateDay = Date()
                        let dateFormatterDay = DateFormatter()
                        dateFormatterDay.dateFormat = "DD"
                        let dateByDay = dateFormatterDay.string(from: dateDay)
                        print(dateByDay)

今年到目前为止的总月数：

 let dateMonth = Date()
                        let dateFormatterMonth = DateFormatter()
                        dateFormatterMonth.dateFormat = "MM"
                        let dateByMonth = dateFormatterMonth.string(from: dateMonth)
                        print(dateByMonth)

Answer 1

请尝试以下代码段。它是用Swift 3和Swift 4编写的。

let calendar = Calendar.current
let weekOfYear = calendar.component(.weekOfYear, from: Date())
print(weekOfYear)

这将打印一年中的总周数。

Answer 2

在今天的日期使用它：

Calendar.current.ordinality(of: .weekOfYear, in: .year, for: Date())!

同样，您可以在一年中的某一天使用它：

Calendar.current.ordinality(of: .day, in: .year, for: self)!

或者当前月份：

Calendar.current.ordinality(of: .month, in: .year, for: self)!

你也可以在Date上将它们定义为扩展：

extension Date {
    public var dayOfYear: Int {
        return Calendar.current.ordinality(of: .day, in: .year, for: self)!
    }
    public var weekOfYear: Int {
        return Calendar.current.ordinality(of: .weekOfYear, in: .year, for: self)!
    }
    public var monthOfYear: Int {
        return Calendar.current.ordinality(of: .month, in: .year, for: self)!
    }
}

let nowDate = Date() //"Sep 3, 2018 at 10:54 AM"
nowDate.dayOfYear    //246
nowDate.weekOfYear   //36
nowDate.monthOfYear  //9

Answer 3

extension Date{
    var weekOfYear: Int {
        return Calendar.current.component(.weekOfYear,  from: self)
    }
}

用法：

print("WeakOfYear :: ", Date().weekOfYear)