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我创建了一个从 NSString 返回 NSDate 的方法。代码如下。我发送到函数“2/25/2011”。函数返回“2010-12-26 08:00:00 +0000”

我做错什么了?还有我需要在最后释放的 NSString。我怎么做?

谢谢你!

-(NSDate *) GetDatefromString:(NSString *) Str
{

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

    [formatter setDateFormat:@"MM-dd-YYYY"];

    NSDate *dateFromString;
            // = [[NSDate alloc] init]; tried taking this part out but still not working


    if (Str != NULL)
    {
        dateFromString = [formatter dateFromString:Str];

    }
    else
    {
        dateFromString = [formatter dateFromString:@"1/1/1970"];
    }

    [formatter release];

     return dateFromString;    

// how do I release dateFromString?

  /*  
    Printing description of dateFromString:
    2010-12-26 08:00:00 +0000
    Printing description of Str:
    02-25-2011
  */  
}
4

3 回答 3

2

您正在使用/分隔符传入日期,但您指定-为日期格式化程序的分隔符。至于您关于释放字符串的问题,您应该只释放您拥有的对象,即您使用newalloccopy或创建的对象mutableCopy。请参阅下面的示例。

NSDateFormatter* formatter = [[NSDateFormatter alloc] init]; // needs releasing
[formatter setDateFormat:@"MM-dd-yyyy"];

NSString* str1 = @"06/25/2011"; // does not need releasing
NSString* str2 = [[NSString alloc] initWithString:@"06-25-2011"]; // needs releasing

NSDate* date1 =  [formatter dateFromString:str1]; // does not need releasing
NSDate* date2 =  [[NSDate alloc] init]; // needs releasing
date2 = [formatter dateFromString:str2]; 

NSLog(@"date from %@ : %@", str1, date1);
NSLog(@"date from %@ : %@", str2, date2);

// release the objects you own
[formatter release];
[str2 release];
[date2 release];

// prints out
date from 06/25/2011 : (null)
date from 06-25-2011 : 2011-06-25 00:00:00 -0700
于 2011-06-25T23:34:04.427 回答
1

您将格式设置为,@"MM-dd-YYYY"但您传入的字符串的格式为@"1/1/1970". 那不匹配。请参阅数据格式化指南:日期格式化程序


// how do I release dateFromString?

使用自动释放

return [dateFromString autorelease];

请参阅内存管理

于 2011-06-25T22:55:47.410 回答
1

我遇到的问题是格式有一年的大写字母。

这是对的:

 [formatter setDateFormat:@"MM/dd/yyyy"];

这是错误的:注意大写字母 YYYY

[formatter
setDateFormat:@"MM-dd-YYYY"];
于 2011-06-26T03:42:36.530 回答