I have a problem. I want to create a file like XML. I have create a code for this but the file not append the information but rewrite and save only the last NSData. Can you help me/ This is my code

-(void)salvataggioInXML:(NSString*)name:(float)x:(float)y:(float)z{

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,  NSUserDomainMask, YES);
 NSString *documentsDirectoryPath = [paths objectAtIndex:0];
 NSString *filePath = [documentsDirectoryPath  stringByAppendingPathComponent:@"filePosizioni.xml"];
 NSFileHandle *myHandle = [NSFileHandle fileHandleForUpdatingAtPath:filePath];
 [myHandle seekToEndOfFile];

 NSString *tagName = [NSString stringWithFormat:@"<name>%@<name>", name];
 NSString *tagX = [NSString stringWithFormat:@"<x>%f<x>", name];
 NSString *tagY = [NSString stringWithFormat:@"<y>%f<y>", name];
 NSString *tagZ = [NSString stringWithFormat:@"<z>%f<z>", name];

 NSData* dataName = [tagName dataUsingEncoding: NSASCIIStringEncoding];
 NSData* dataX = [tagX dataUsingEncoding: NSASCIIStringEncoding];
 NSData* dataY = [tagY dataUsingEncoding: NSASCIIStringEncoding];
 NSData* dataZ = [tagZ dataUsingEncoding: NSASCIIStringEncoding];

 if ([dataName writeToFile:filePath atomically:YES])
  NSLog(@"writeok");


    [myHandle seekToEndOfFile];
 if ([dataX writeToFile:filePath atomically:YES]) 
        NSLog(@"writeok");

 [myHandle seekToEndOfFile];
 if ([dataY writeToFile:filePath atomically:YES])
  NSLog(@"writeok");


    [myHandle seekToEndOfFile];
 if ([dataZ writeToFile:filePath atomically:YES])    
  NSLog(@"writeok");


    [myHandle seekToEndOfFile];

 NSLog(@"zp26 %@",filePath);   
}