ios – 获得firstdate,月份的最后日期

这是一个简单的方法来找到一个月的开始：

(NSDate *) startOfMonth
{
    NSCalendar * calendar = [NSCalendar currentCalendar];

    NSDateComponents * currentDateComponents = [calendar components: NSYearCalendarUnit | NSMonthCalendarUnit fromDate: self];
    NSDate * startOfMonth = [calendar dateFromComponents: currentDateComponents];

    return startOfMonth;
}

所有这一切都是从当天开始的年份和月份组件,然后再次转换为日期.

在本月底,我使用了几种方法：

- (NSDate *) dateByAddingMonths: (NSInteger) monthsToAdd
{
    NSCalendar * calendar = [NSCalendar currentCalendar];

    NSDateComponents * months = [[NSDateComponents alloc] init];
    [months setMonth: monthsToAdd];

    return [calendar dateByAddingComponents: months toDate: self options: 0];
}

和

- (NSDate *) endOfMonth
{
    NSCalendar * calendar = [NSCalendar currentCalendar];

    NSDate * plusOneMonthDate = [self dateByAddingMonths: 1];
    NSDateComponents * plusOneMonthDateComponents = [calendar components: NSYearCalendarUnit | NSMonthCalendarUnit fromDate: plusOneMonthDate];
    NSDate * endOfMonth = [[calendar dateFromComponents: plusOneMonthDateComponents] dateByAddingTimeInterval: -1]; // One second before the start of next month

    return endOfMonth;
}

这是一个3步的过程 – 在当前日期添加一个月,找到下个月的开始,然后减去1秒,以找到本月底.

Swift 3

extension Date {

    func startOfMonth() -> Date? {

        let calendar = Calendar.current
        let currentDateComponents = calendar.dateComponents([.year,.month],from: self)
        let startOfMonth = calendar.date(from: currentDateComponents)

        return startOfMonth
    }

    func dateByAddingMonths(_ monthsToAdd: Int) -> Date? {

        let calendar = Calendar.current
        var months = DateComponents()
        months.month = monthsToAdd

        return calendar.date(byAdding: months,to: self)
    }

    func endOfMonth() -> Date? {

        guard let plusOneMonthDate = dateByAddingMonths(1) else { return nil }

        let calendar = Calendar.current
        let plusOneMonthDateComponents = calendar.dateComponents([.year,from: plusOneMonthDate)
        let endOfMonth = calendar.date(from: plusOneMonthDateComponents)?.addingTimeInterval(-1)

        return endOfMonth

    }
}

斯威夫特2

extension NSDate {

    func startOfMonth() -> NSDate? {

        let calendar = NSCalendar.currentCalendar()
        let currentDateComponents = calendar.components(.CalendarUnitYear | .CalendarUnitMonth,fromDate: self)
        let startOfMonth = calendar.dateFromComponents(currentDateComponents)

        return startOfMonth
    }

    func dateByAddingMonths(monthsToAdd: Int) -> NSDate? {

        let calendar = NSCalendar.currentCalendar()
        let months = NSDateComponents()
        months.month = monthsToAdd

        return calendar.dateByAddingComponents(months,toDate: self,options: nil)
    }

    func endOfMonth() -> NSDate? {

        let calendar = NSCalendar.currentCalendar()
        if let plusOneMonthDate = dateByAddingMonths(1) {
            let plusOneMonthDateComponents = calendar.components(.CalendarUnitYear | .CalendarUnitMonth,fromDate: plusOneMonthDate)

            let endOfMonth = calendar.dateFromComponents(plusOneMonthDateComponents)?.dateByAddingTimeInterval(-1)

            return endOfMonth
        }

        return nil
    }
}