查找任何日期的下一个最接近的特定日期的NSDate [英] Find NSDate for the next closest specific day of week for any date

问题描述

假设今天是星期三。我可以将 NSDate 分解为 NSDateComponents ，但是我需要找到 NSDate 和下一个即将星期一。如果今天是星期一，那么下一个即将到来的星期一是今天。实现此目标的正确方法是什么？

Let's suppose that today is Wednesday. I can break an NSDate down into NSDateComponents, but I need to find the NSDate with the next upcoming Monday. If today is Monday, then the next upcoming Monday is today. What's the right way to achieve this?

推荐答案

您可以使用 nextDateAfterDate：方法在 NSCalendar 对象上实现，

You can use nextDateAfterDate: method on NSCalendar object to achieve this,

let now = Date() // today

var matchingComponents = DateComponents()
matchingComponents.weekday = 2 // Monday

let comingMonday =  Calendar.current.nextDate(after: now,
                                              matching: matchingComponents,
                                              matchingPolicy:.nextTime)

此处，是下周一查找的简单方法。如果今天是星期一，则以下函数今天返回，否则返回下一个星期一。请注意，它使用 en_POSIX_US ，以便可以匹配日期。当语言环境为 en_POSIX_US 时，工作日符号变为

Here, is a simple method to find next monday. If today is Monday the following function returns today or else the closest next Monday. Note that it uses en_POSIX_US such that the days can be matched. When the locale is en_POSIX_US, weekdays symbols become,

["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]

，以下是这几天的使用方式。

And, here is how this days could be used,

func findNext(_ day: String, afterDate date: Date) -> Date? {

    var calendar = Calendar.current
    calendar.locale = Locale(identifier: "en_US_POSIX")

    let weekDaySymbols = calendar.weekdaySymbols
    let indexOfDay = weekDaySymbols.index(of: day)

    assert(indexOfDay != nil, "day passed should be one of \(weekDaySymbols), invalid day: \(day)")

    let weekDay = indexOfDay! + 1

    let components = calendar.component(.weekday, from: date)

    if components == weekDay {
        return date
    }

    var matchingComponents = DateComponents()
    matchingComponents.weekday = weekDay // Monday

    let nextDay = calendar.nextDate(after: date,
                                    matching: matchingComponents,
                                    matchingPolicy:.nextTime)
    return nextDay!
}


let nextMonday = findNext("Monday", afterDate: Date())
let mondayAfterThat = findNext("Monday", afterDate: nextMonday!)

let thursday = findNext("Thursday", afterDate: mondayAfterThat!)

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