iOS NSString与NSDate互相转换及NSDate比较

由 NSDate 转换为 NSString:

1. NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
2. [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
3. NSString *strDate = [dateFormatter stringFromDate:[NSDate date]];
4. NSLog(@"%@", strDate);

结果:

1. 2015-06-14 13:01:03

由 NSString 转换为 NSDate:

1. NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
2. [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
3. NSDate *date = [dateFormatter dateFromString:@"2010-08-04 16:01:03"];
4. NSLog(@"%@", date);

结果:

1. 2015-06-14 13:01:03 +0800

日期之间比较可用以下方法

    - (BOOL)isEqualToDate:(NSDate *)otherDate;

    与otherDate比较，相同返回YES

    - (NSDate *)earlierDate:(NSDate *)anotherDate;

    与anotherDate比较，返回较早的那个日期

    - (NSDate *)laterDate:(NSDate *)anotherDate;

    与anotherDate比较，返回较晚的那个日期

    - (NSComparisonResult)compare:(NSDate *)other;

    该方法用于排序时调用:

      . 当实例保存的日期值与anotherDate相同时返回NSOrderedSame

      . 当实例保存的日期值晚于anotherDate时返回NSOrderedDescending

      . 当实例保存的日期值早于anotherDate时返回NSOrderedAscending