Here is a little sample to write/read files with objective c on native Iphone Application.
This snippet write into the Document Directory of the application. We will see later problems when trying to write in the Resources folder


WRITE

NSString *dataStr = @"my data";

//get Document Root
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

//append file name to path	
NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"myFile"];

//prepar data in A NSData from a String
NSData *aData = [dataStr dataUsingEncoding: NSUTF8StringEncoding];

//Write to the file.
//File will be automacally created if not exist
[aData writeToFile:filePath atomically:YES];

READ

//get Document root
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
	
NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"myFile"];
NSString *myText = [NSString stringWithContentsOfFile:filePath]; 
if (myText) {
    return myText;
} else  {
    //can not read because file does not exists
    //make here your error handler 
}

WARNING : It is possible to get a file from Resources Folder with the follwing line :

NSString *filePath = [[NSBundle mainBundle] pathForResource:fileName ofType:extension];

Be carreful with that because if the file does not exist filePath will be null, so it will be impossible to create the file... difficult to write into the file :p