NSString与NSDate互相转换

转载地址 http://blog.sina.com.cn/s/blog_6d01cce3010199if.html
由NSDate
转换为NSString:

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

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

NSString*strDate = [dateFormatter stringFromDate:[NSDatedate]];

NSLog(@"%@",strDate);

[dateFormatterrelease];

结果:

2010-08-0416:01:03

由NSString
转换为NSDate:

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

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

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

NSLog(@"%@",date);

[dateFormatterrelease];

结果:

2010-08-0416:01:03 +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