NSString与NSDate互相转换及NSDate…

由 NSDate 转换为 NSString:

NSDateFormatter *dateFormatter =
[[NSDateFormatter alloc] init];

[dateFormatter
setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

NSString *strDate = [dateFormatter
stringFromDate:[NSDate date]];

NSLog(@"%@", strDate);

[dateFormatter
release];

结果:

2010-08-04 16:01:03

由 NSString 转换为 NSDate:

NSDateFormatter *dateFormatter =
[[NSDateFormatter alloc] init];

[dateFormatter
setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

NSDate *date = [dateFormatter
dateFromString:@"2010-08-04 16:01:03"];

NSLog(@"%@", date);

[dateFormatter
release];

结果:

2010-08-04 16:01:03
+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