查找任何日期的下一个最接近的特定星期几的 NSDate

Question

假设今天是星期三。我可以将 NSDate 分解为 NSDateComponents，但我需要在下一个 即将到来的 星期一找到 NSDate。如果今天是星期一，那么下一个 即将到来的 星期一就是今天。实现这一目标的正确方法是什么？

Answer 1

您可以使用 NSDateComponents 获取工作日并计算间隔天数，然后使用 NSDate 中的 dateByAddingTimeInterval ，如下所示：

let now = NSDate()
let calendar: NSDateComponents = NSCalendar.currentCalendar().components(NSCalendarUnit.CalendarUnitWeekday, fromDate: now)
let weekday = calendar.weekday  // 1 = Sunday, 2 = Monday

// You get input the weekday here and calculate the interval

// exmaple for moving to the next day
let expectedDate = now.dateByAddingTimeInterval(1 * 24 * 60 * 60)

// exmaple for moving to yesterday
let yesterday = now.dateByAddingTimeInterval(-1 * 24 * 60 * 60)

Answer 2

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)

这里是一个简单的查找下周一的方法。如果今天是星期一，则以下函数 returns 今天或最近的下星期一。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，这几天可以这样使用，

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!)

Answer 3

对于目标 iOS >= 8 使用 GeneratorOfOne 的解决方案

否则你可以使用这个

let now = NSDate()
var lastMonday:NSDate?
var nextMonday:NSDate?
var start:NSDate?        

var interval:NSTimeInterval = 0   // holds the length of a week. can differ for Daylight Saving Time
let cal = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)! // have a own calendar object for this calculation to guarantee that the next line does not influence other calculations 
cal.firstWeekday = 2              // make sure first day of week is Monday. 


cal.rangeOfUnit(NSCalendarUnit.CalendarUnitWeekOfMonth, startDate: &lastMonday, interval:&interval, forDate: now)      // monday of current week
nextMonday = lastMonday?.dateByAddingTimeInterval(interval)  // add a weeks length to the last weeks's monday
println(nextMonday)

查找任何日期的下一个最接近的特定星期几的 NSDate

Find NSDate for the next closest specific day of week for any date

cocoa

cocoa-touch

nsdate

date-arithmetic