[NSCFString timeIntervalSinceReferenceDate]：发送到实例的无法识别的选择器
我想比较两个日期之间的差异，但使用下面的代码我收到错误“[NSCFString timeIntervalSinceReferenceDate]：无法识别的选择器发送到实例。”代码有什么问题吗？
NSDate *dateAdded=[eventDictionary objectForKey:@"dateAdded"];
NSDate *validUntilDate=[eventDictionary objectForKey:@"validUntilDate"];
NSDateComponents *sometimeAgo = [[NSCalendar currentCalendar] components:(NSSecondCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:dateAdded toDate:validUntilDate options:0];
I would like to compare difference between two dates, but with the code below I got the error "[NSCFString timeIntervalSinceReferenceDate]: unrecognized selector sent to instance." What's wrong with the code?
NSDate *dateAdded=[eventDictionary objectForKey:@"dateAdded"];
NSDate *validUntilDate=[eventDictionary objectForKey:@"validUntilDate"];
NSDateComponents *sometimeAgo = [[NSCalendar currentCalendar] components:(NSSecondCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:dateAdded toDate:validUntilDate options:0];
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看起来
dateAdded和/或validUntilDate实际上是字符串而不是日期。也许它们是代表日期的字符串，但毕竟是字符串。It looks like
dateAddedand/orvalidUntilDateare actually strings and not dates. Maybe they are strings representing dates, but strings after all.您需要使用 NSDateFormatter 将日期字符串转换为实际的 NSDates。
You need to use an NSDateFormatter to convert your date strings to actual NSDates.