如何将NSDate转换为相对格式为"今天","昨天","一周前","一个月前","一年前"？

我想将nsdate转换为相对格式"Today","Yesterday","a week ago","a month ago","a year ago","date as it is".

我已经为它写了以下方法..但有些如何只是打印,因为它是日期..你能告诉我应该是什么问题吗？

//以下是我的函数,它将日期转换为相对字符串

+(NSString *)getDateDiffrence:(NSDate *)strDate{
    NSDateFormatter *df = [[NSDateFormatter alloc] init];

    df.timeStyle = NSDateFormatterMediumStyle;
    df.dateStyle = NSDateFormatterShortStyle;
    df.doesRelativeDateFormatting = YES;
    NSLog(@"STRING DATEEE : %@ REAL DATE TODAY %@",[df stringFromDate:strDate],[NSDate date]);
      return [df stringFromDate:strDate];

}

我有以下格式的日期字符串 "2013-10-29T09:38:00"

当我试图给出NSDate对象时,它总是返回我的null日期.
所以我试图将该日期转换为yyyy-MM-dd HH:mm:ssZZZZ然后我将此日期传递给函数然后它只是打印整个日期..

如何解决这个问题呢？

//以下是我调用上述函数的代码

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss"];
NSDate *date = [formatter dateFromString:[threadDict objectForKey:@"lastMessageDate"]];
[formatter setDateFormat:@"yyyy-MM-dd HH:mm:ssZZZZ"];

NSString *date1 = [formatter stringFromDate:date];
NSDate *date_d = [formatter dateFromString:date1];
NSString *resultstr=[UserManager getDateDiffrence:date];

self.dateLabel.text=resultstr;

David Rönnqv.. 56

为简单起见,我假设你格式化的日期都是过去的(没有"明天"或"下周").并不是说它不能完成,而是处理更多的情况并返回更多的字符串.

您可以使用所需components:fromDate:toDate:options:的任何日期组件组合来获取两个日期之间的年数,月数,周数,天数,小时数等.然后,按照从最重要(例如年份)到最不重要(例如日)的顺序浏览它们,您可以仅基于最重要的组件格式化字符串.

例如:1周,2天和7小时前的日期将被格式化为"1周".

如果要为特定数量的单元创建特殊字符串,例如"明天"为"1天前",则可以在确定该组件是最重要的组件后检查该组件的值.

代码看起来像这样:

- (NSString *)relativeDateStringForDate:(NSDate *)date
{
    NSCalendarUnit units = NSCalendarUnitDay | NSCalendarUnitWeekOfYear | 
                           NSCalendarUnitMonth | NSCalendarUnitYear;

    // if `date` is before "now" (i.e. in the past) then the components will be positive
    NSDateComponents *components = [[NSCalendar currentCalendar] components:units
                                                                   fromDate:date
                                                                     toDate:[NSDate date]
                                                                    options:0];

    if (components.year > 0) {
        return [NSString stringWithFormat:@"%ld years ago", (long)components.year];
    } else if (components.month > 0) {
        return [NSString stringWithFormat:@"%ld months ago", (long)components.month];
    } else if (components.weekOfYear > 0) {
        return [NSString stringWithFormat:@"%ld weeks ago", (long)components.weekOfYear];
    } else if (components.day > 0) {
        if (components.day > 1) {
            return [NSString stringWithFormat:@"%ld days ago", (long)components.day];
        } else {
            return @"Yesterday";
        }
    } else {
        return @"Today";
    }
}

如果您的日期也可以在将来,那么您可以按相同的顺序检查组件的绝对值,然后检查它是正还是负,以返回相应的字符串.我只展示下面的一年:

if ( abs(components.year > 0) ) { 
    // year is most significant component
    if (components.year > 0) {
        // in the past
        return [NSString stringWithFormat:@"%ld years ago", (long)components.year];
    } else {
        // in the future
        return [NSString stringWithFormat:@"In %ld years", (long)components.year];
    }
} 

对于时差只是好处但今天/昨天不起作用,因为如果它在过去24小时内被认为是今天:/ (6认同)

您不应该将`%zd`用于`NSDateComponents`的各种属性,因为`NSDateComponents`的属性使用`NSInteger`,而不是`size_t`.[字符串编程指南](https://developer.apple.com/library/ios/documentation/cocoa/conceptual/Strings/Articles/formatSpecifiers.html#//apple_ref/doc/uid/TP40004265-SW5)建议使用` %ld`并转换为`long`.在64位平台上,演员将成为无操作. (3认同)

ChrisJF.. 13

这是我的回答(在Swift 3中!)以及为什么它更好.

回答:

func datePhraseRelativeToToday(from date: Date) -> String {

    // Don't use the current date/time. Use the end of the current day 
    // (technically 0h00 the next day). Apple's calculation of 
    // doesRelativeDateFormatting niavely depends on this start date.
    guard let todayEnd = dateEndOfToday() else {
        return ""
    }

    let calendar = Calendar.autoupdatingCurrent

    let units = Set([Calendar.Component.year,
                 Calendar.Component.month,
                 Calendar.Component.weekOfMonth,
                 Calendar.Component.day])

    let difference = calendar.dateComponents(units, from: date, to: todayEnd)

    guard let year = difference.year,
        let month = difference.month,
        let week = difference.weekOfMonth,
        let day = difference.day else {
            return ""
    }

    let timeAgo = NSLocalizedString("%@ ago", comment: "x days ago")

    let dateFormatter: DateFormatter = {
        let formatter = DateFormatter()
        formatter.locale = Locale.autoupdatingCurrent
        formatter.dateStyle = .medium
        formatter.doesRelativeDateFormatting = true
        return formatter
    }()

    if year > 0 {
        // sample output: "Jan 23, 2014"
        return dateFormatter.string(from: date)
    } else if month > 0 {
        let formatter = DateComponentsFormatter()
        formatter.unitsStyle = .brief // sample output: "1mth"
        formatter.allowedUnits = .month
        guard let timePhrase = formatter.string(from: difference) else {
            return ""
        }
        return String(format: timeAgo, timePhrase)
    } else if week > 0 {
        let formatter = DateComponentsFormatter()
        formatter.unitsStyle = .brief; // sample output: "2wks"
        formatter.allowedUnits = .weekOfMonth
        guard let timePhrase = formatter.string(from: difference) else {
            return ""
        }
        return String(format: timeAgo, timePhrase)
    } else if day > 1 {
            let formatter = DateComponentsFormatter()
            formatter.unitsStyle = .abbreviated; // sample output: "3d"
            formatter.allowedUnits = .day
            guard let timePhrase = formatter.string(from: difference) else {
                return ""
            }
            return String(format: timeAgo, timePhrase)
    } else {
        // sample output: "Yesterday" or "Today"
        return dateFormatter.string(from: date)
    }
}

func dateEndOfToday() -> Date? {
    let calendar = Calendar.autoupdatingCurrent
    let now = Date()
    let todayStart = calendar.startOfDay(for: now)
    var components = DateComponents()
    components.day = 1
    let todayEnd = calendar.date(byAdding: components, to: todayStart)
    return todayEnd
}

请记住重复使用格式化程序以避免任何性能损失!提示:DateFormatter和DateComponentsFormatter上的扩展是好主意.

为什么它更好:

利用DateFormatter的"昨天"和"今天".这已经由Apple翻译,可以为您节省工作!

使用DateComponentsFormatter已翻译的"1周"字符串.(再次为你工作,Apple的礼貌.)你所要做的就是翻译"%@ ago"字符串.

其他答案错误地计算了当天从"今天"切换到"昨天"等的时间.固定常数是一个很大的NO-NO,因为原因.此外,其他答案使用当前日期/时间,他们应该使用当天日期/时间的结束.

使用autoupdatingCurrent进行日历和区域设置,确保您的应用程序立即与Settings.app中的用户日历和语言首选项保持同步

这个答案的灵感来自于GitHub上的DateTools.