如何将日期字符串转换为字符串（yyyy-MM-dd）。当这样做，我得到null值？ [英] How to convert the date string into string( yyyy-MM-dd). While doing so, I getting null values?

问题描述

我有数据作为customerFromDate01 Apr 2010和customerToDate2010年4月30日这是一个字符串。

I have the data as customerFromDate " 01 Apr 2010 " and customerToDate " 30 Apr 2010 " which is a string.

我想将该格式转换为字符串yyyy-MM-dd，但是当这样做时，我获得了空值。
请参阅我尝试的以下代码。

I want to convert that format into the string "yyyy-MM-dd", but when doing so I got null values. Please see the following code which I had tried.

printf("\n customerFromDate %s",[customerStatementObj.customerFromDate UTF8String]);
printf("\n customerToDate %s",[customerStatementObj.customerToDate UTF8String]);
/*
 prints as the following 
 customerFromDate 01 Apr 2010
 customerToDate 30 Apr 2010
 */

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:@"yyyy-MM-dd"];
NSDate *fromDate=[[NSDate alloc]init];
fromDate = [dateFormatter dateFromString:customerStatementObj.customerFromDate];
printf("\n fromDate: %s",[fromDate.description UTF8String]);
NSString *fromDateString=[dateFormatter stringFromDate:fromDate];
printf("\n fromDateString: %s",[fromDateString UTF8String]);    
[dateFormatter release];

NSDateFormatter *dateFormatter1 = [[NSDateFormatter alloc]init];
[dateFormatter1 setDateFormat:@"yyyy-MM-dd"];
NSDate *toDate=[[NSDate alloc]init];
toDate = [dateFormatter1 dateFromString:customerStatementObj.customerToDate];
printf("\n toDate: %s",[toDate.description UTF8String]);
NSString *toDateString=[dateFormatter1 stringFromDate:toDate];
printf("\n toDateString: %s",[toDateString UTF8String]);            
[dateFormatter1 release];

谢谢你，
Madan Mohan。

Thank you, Madan Mohan.

推荐答案

几个注释：

您需要两个不同的NSDateFormatter。一个指定输入日期格式，另一个指定输出日期格式。

You need two different NSDateFormatters. One that specifies the input date format, and one that specifies the output date format.

    NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
    [inputFormatter setDateFormat:@"dd MMM yyyy"];
    NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
    [outputFormatter setDateFormat:@"yyyy-MM-dd"];

您可以为 fromDate toDate 。

其次， dateFromString：返回已分配的自动释放的NSDate对象。您泄漏的是您手动分配的。

Secondly, dateFromString: returns an allocated, autoreleased NSDate object. You are leaking the ones you manually allocate.

#import <Cocoa/Cocoa.h>

int main (int argc, char const *argv[])
{
    NSAutoreleasePool *pool = [NSAutoreleasePool new];

    NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
    [inputFormatter setDateFormat:@"dd MMM yyyy"];
    NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
    [outputFormatter setDateFormat:@"yyyy-MM-dd"];

    NSDate *fromDate = [inputFormatter dateFromString:@"01 Apr 2010"];
    NSDate *toDate = [inputFormatter dateFromString:@"30 Apr 2010"];

    printf("\n fromDate: %s",[fromDate.description UTF8String]);
    NSString *fromDateString=[outputFormatter stringFromDate:fromDate];
    printf("\n fromDateString: %s",[fromDateString UTF8String]);

    printf("\n toDate: %s",[toDate.description UTF8String]);
    NSString *toDateString=[outputFormatter stringFromDate:toDate];
    printf("\n toDateString: %s",[toDateString UTF8String]);

    [inputFormatter release];
    [outputFormatter release];

    [pool drain];
    return 0;
}

这篇关于如何将日期字符串转换为字符串（yyyy-MM-dd）。当这样做，我得到null值？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！