ios - NSDate 返回小时/天/周

Question

Instagram程序中的快照，日期显示为（例如）2小时前/3天前/1周前..我有“2013-03-20 16:02:48”..我怎样才能得到字符串“2天前“？

Answer 1

考虑使用NSCalendar和NSDateComponents来计算差异并与最终用户相似。

Answer 2

有一个开源项目

https://github.com/billgarrison/SORelativeDateTransformer

从其文档中：

例如，当前日期时间为 2010-12-05 11:30，则
... 2010-12-05 11:00 转换为“30 分钟前”
... 2010-12-01 11:00转换为“5天前”
... 2010-12-25 08:00 转换为“2周内”

// Display a file's creation date relative to today's date
NSURL *someFilePath = ...;
NSDictionary *attribs = [[NSFileManager defaultManager] attributesOfItemAtPath:someFilePath error:NULL];

NSDate *dateModified = [attribs fileModificationDate];

// fileModificationDate is 2010-10-01 12:00:00TZ; 
// Date now is 2010-10-30 12:00:00TZ

SORelativeDateTransformer *relativeDateTransformer = [[SORelativeDateTransformer alloc] init];
NSString *relativeDate = [relativeDateTransformer transformedValue: dateModified];

NSLog (@"This file was modified %@.", relativeDate); // ==> "This file was modified 3 weeks ago."

Answer 3

也许某处有一个图书馆可以为您做到这一点。

但无论如何，这并不难。可以将 NSDate 分解为其组件。然后很容易比较它们并编写一些 if then else 代码来涵盖所有需要的情况。

这是我的一个项目中的一个示例，我在过去 7 天内将日期解析为适当的工作日：

NSString *resultDateString;

// First, reduce the two dates we want to compare to the scope of days by erasing hours, minutes and seconds

unsigned int flagA = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
NSDateComponents *compsA = [[NSCalendar currentCalendar] components:flagA fromDate:myObjectsDate];
[compsA setHour:0];
[compsA setMinute:0];
[compsA setSecond:0];
NSDate *checkDate = [[NSCalendar currentCalendar] dateFromComponents:compsA];

unsigned int flagB = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
NSDateComponents *partsB = [[NSCalendar currentCalendar] components:flagB fromDate:[NSDate date]];
[compsB setHour:0];
[compsB setMinute:0];
[compsB setSecond:0];
NSDate *nowDate = [[NSCalendar currentCalendar] dateFromComponents:compsB];

// Get the interval between the two dates, interval is still in seconds, but since it is calculated using days only, it will be precisely 0 if the day is the same    

NSTimeInterval interval = [searchDate timeIntervalSinceDate:nowDate];

// check if the objects date is today. If it isn't, find out which day it is and name it appropriately

if (interval == 0) {

    resultDateString = [NSString stringWithString:@"Today"];

} else {

   unsigned int flagC = NSWeekdayCalendarUnit;
   NSDateComponents *compsC = [[NSCalendar currentCalendar] components:flagC fromDate:myObjectsDate];

   switch ([compsC weekday]) {
       case 1:
           resultDateString = @"Sunday";
           break;
       case 2:
           resultDateString = @"Monday";
           break;
       case 3:
           resultDateString = @"Tuesday";
           break;
       case 4:
           resultDateString = @"Wednesday";
           break;
       case 5:
           resultDateString = @"Thursday";
           break;
       case 6:
           resultDateString = @"Friday";
           break;
       case 7:
           resultDateString = @"Saturday";
           break;

       default:
           break;
   }

}

这只是一个摘录，请注意，此代码片段不会检查间隔是否长于 7 天，因为我在代码中以不同的方式涵盖了此类情况。但我认为它会给你一个如何做到这一点的基本概念。