在Objective-C(iPhone)中将字符串保存到文件中

我似乎遇到了一个从字符串中保存XML文件的问题(这是在iPhone上完成的) 文件本身存在并包含在项目中(因此在工作区中),我从下面的代码片段中得到的所有指示在模拟器上无任何错误地通过,在iPhone上失败(错误513),但在这两种情况下,文件都不会被保存!

{
Hits = config->Hits;

NSString*   filenameStr = [m_FileName stringByAppendingFormat: @".xml" ]; 
NSString*   pData = [self getDataString];  // write xml format - checked out ok
NSError     *error;

/* option 2 - does not work as well
 NSBundle        *mainBundle = [NSBundle mainBundle];
 NSURL           *xmlURL = [NSURL fileURLWithPath:[mainBundle pathForResource: m_FileName ofType: @"xml"]];

 if(![pData writeToURL: xmlURL atomically: true encoding:NSUTF8StringEncoding error:&error]) 
 {
 NSLog(@"Houston - we have a problem %s@\n",[error localizedFailureReason]);
 return false;
 }
 */

if(![pData writeToFile: filenameStr atomically: FALSE encoding:NSUTF8StringEncoding error:&error]) 
{
    NSLog(@"Houston - we have a problem %s@\n",[error localizedFailureReason]);
    return false;
}
return true;

}

如有任何帮助,我们将不胜感激, -A