如何从NSDate计算年龄

问题描述

我正在制作一个应用程序，需要根据他们的生日找到某人的年龄。我有一个简单的 NSDate 但我如何用 NSDateFormatter 找到它？

I am working on an app that needs to find someones age depending on their birthday. I have a simple NSDate but how would I find this with NSDateFormatter?

推荐答案

- (NSInteger)ageFromBirthday:(NSDate *)birthdate {
    NSDate *today = [NSDate date];
    NSDateComponents *ageComponents = [[NSCalendar currentCalendar]
                                       components:NSCalendarUnitYear
                                       fromDate:birthdate
                                       toDate:today
                                       options:0];
    return ageComponents.year;
}

NSDateFormatter 适用于格式化日期（呃！）。根据经验，只要您需要在 NSDate 上执行某些计算，就可以使用 NSCalendar 和相关联的类，例如 NSDateComponents 。

NSDateFormatter is for formatting dates (duh!). As a rule of thumb, whenever you need to perform some computation on an NSDate you use a NSCalendar and associated classes, such as NSDateComponents.

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