Swift

Question

我需要一种方法来打印今年到目前为止的周数。
我已经设法打印了天数和月数（见下面的代码）。
但无法弄清楚如何对总周数执行相同的操作。

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

今天的约会用这个：

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

同样，您可以将它用于一年中的某一天：

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

或当前月份：

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

您还可以将这些定义为 Date 的扩展：

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 2

试试下面的代码片段。写在Swift3和Swift4.

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 3

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

用法：

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

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