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NSDate为该月的第一天

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这是一个非常简单的概念，但到目前为止，我一直无法找到一个优雅的（和日历区域独立）解决方案 . 我需要在一个月的第一天找到任意的 NSDate . 例如，给定一个任意的 NSDate （ arbitraryDate ），将返回另一个NSDate对象（让我们称之为 firstDayOfMonthDate ），它代表 arbitraryDate 中该月的第一天 . 时间组件并不重要，因为我只需要在该月的第一天使用NSDate对象（尽管为了整洁，如果时间刚刚归零，它将是有用的） .

在此先感谢您的任何帮助 .

iphone cocoa-touch nsdate nscalendar

5 回答

  • 1

    可能的解决方案：

    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *arbitraryDate = [NSDate date];
NSDateComponents *comp = [gregorian components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:arbitraryDate];
[comp setDay:1];
NSDate *firstDayOfMonthDate = [gregorian dateFromComponents:comp];
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  • 1
    NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear 
                                                               fromDate:[NSDate date]];
components.day = 1;
NSDate *firstDayOfMonthDate = [[NSCalendar currentCalendar] dateFromComponents: components];
NSLog(@"First day of month: %@", [firstDayOfMonthDate descriptionWithLocale:[NSLocale currentLocale]]);
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  • 4

    Swift 3

    我已经包括了这个月的最后一天，以防它对任何人都有用 .

    extension Date {
    func lastDayOfMonth() -> Date {
        let calendar = Calendar.current
        let dayRange = calendar.range(of: .day, in: .month, for: self)
        let dayCount = dayRange!.count
        var comp = calendar.dateComponents([.year, .month, .day], from: self)

        comp.day = dayCount

        return calendar.date(from: comp)!
    }

    func firstDayOfMonth() -> Date {
        let calendar: Calendar = Calendar.current
        var components: DateComponents = calendar.dateComponents([.year, .month, .day], from: self)
        components.setValue(1, for: .day)
        return calendar.date(from: components)!
    }
}
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  • 7

    Swift版本

    let arbitraryDate:NSDate = NSDate()
let calendar:NSCalendar = NSCalendar.currentCalendar()
let components:NSDateComponents = calendar.components([.Year, .Month, .Day], fromDate: arbitraryDate)
components.setValue(1, forComponent: .Day)
let firstDayOfMonthDate = calendar.dateFromComponents(components)
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  • 68

    斯威夫特3：

    let calendar = Calendar.current
var comps = calendar.dateComponents([.year, .month], from: date)
comps.setValue(1, for: .day)
let firstDayOfMonth = calendar.date(from: comps)!

// I tried this, but it doesn't work, why?
// let firstDayOfMonth = calendar.date(bySetting: .day, value: 1, of: date)!
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