Ios 无法将文本文件附加到电子邮件

我正在尝试生成一个文本文件并将其附加到电子邮件。以前，我使用此代码将文件附加到电子邮件，并且成功地完成了此操作

 NSString *recipient = @"myemail@me.com";
    NSArray *recipients = [NSArray arrayWithObjects:recipient, nil];

    MFMailComposeViewController *mailViewController = [[MFMailComposeViewController alloc] init];
    mailViewController.mailComposeDelegate = self;
    [mailViewController setSubject:@"Invalid Scan"];
    [mailViewController setToRecipients:recipients];
    [mailViewController setMessageBody:@"" isHTML:NO];
    mailViewController.navigationBar.tintColor = [UIColor blackColor];

    NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

    NSString *textFilePath = [documentsDirectory stringByAppendingFormat:@"/textfile.txt"];
    NSData *myData = [NSData dataWithContentsOfFile:textFilePath];

  //  NSLog(@"my nsdata is %@",myData);

    [mailViewController addAttachmentData:myData
                                 mimeType:@"text/csv"
                                 fileName:textfile.txt];

但当我尝试使用下面的声明时，文件没有附加：

     NSString *fileName_txtFile= @"textfile.txt";
NSString *textFilePath = [documentsDirectory stringByAppendingFormat:[NSString stringWithFormat:@"/%@",fileName_txtFile],nil];
    NSData *myData = [NSData dataWithContentsOfFile:textFilePath];



    [mailViewController addAttachmentData:myData
                                 mimeType:@"text/csv"
                                 fileName:fileName_txtFile];

我不明白为什么文件没有附加到邮件上。你能帮我解决这个问题吗

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提前谢谢

您是否检查过myData是否为零？那么该文件不存在，或者它在设备上有不同的名称大小写。