NSDate和NSString的互相轉換

//輸入的日期字元串形如：@"1992-05-21 13:08:08"

- (NSDate *)dateFromString:(NSString *)dateString{

NSDateFormatter *dateFormatter = [[NSDateFormatteralloc] init];
[dateFormatter setDateFormat: @"yyyy-MM-dd HH:mm:ss"]; 
NSDate *destDate= [dateFormatter dateFromString:dateString];
return destDate;

}

- (NSString *)stringFromDate:(NSDate *)date{

NSDateFormatter *dateFormatter = [[NSDateFormatteralloc] init]; 

//zzz表示時區，zzz可以删除，這樣傳回的日期字元将不包含時區資訊。

[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss zzz"];
NSString *destDateString = [dateFormatter stringFromDate:date];
[dateFormatter release];
return destDateString;
}