cocoa - 查找任意日期下一个最接近的一周中特定日期的 NSDate

Question

假设今天是星期三。我可以将 NSDate 分解为 NSDateComponents，但我需要在下周一即将找到 NSDate。如果今天是星期一，那么下一个即将星期一就是今天。实现这一目标的正确方法是什么？

Answer 1

您可以在 NSCalendar 对象上使用 nextDateAfterDate: 方法来实现此目的，

let now = Date() // today

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

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

这里是一个查找下周一的简单方法。如果今天是星期一，则以下函数返回今天或最接近的下星期一。请注意，它使用 en_POSIX_US 以便可以匹配日期。当区域设置为 en_POSIX_US 时，工作日符号变为，

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

而且，这就是如何利用这几天，

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!)