月末の計算

NSDateから月末を取得する関数を作ってみました。

func endOfMonth(date:NSDate) -> NSDate
{
    let cal = NSCalendar.currentCalendar()
    let flags : NSCalendarUnit = [.Year, .Month, .Day]
    let comps : NSDateComponents = cal.components(flags , fromDate: date)

    var y = comps.year
    var m = comps.month
    m = m + 1
    if (m >= 13) {
        y = y + 1
        m = 1
    }

    let dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd";

    let firstOfMonth : NSDate = dateFormatter.dateFromString("\(y)-\(m)-01")!

    let endOfMonth : NSDate = firstOfMonth.dateByAddingTimeInterval(-60*60*24)

    return endOfMonth
}

使い方

let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd";
let testDate = dateFormatter.dateFromString("2014-2-1")!;
let resOut = endOfMonth(testDate) // "Feb 28, 2014, 12:00 AM"