[[NSFileManager defaultManager] contentsOfDirectoryAtPath:bundleRoot error:nil]

To read the text file using objective c, you need to first get the path and load then load that content into the NSString as given below..

//loading the path
NSString* path = [[NSBundle mainBundle] pathForResource:@"filename" 
                                                 ofType:@"txt"];
//Then loading the content into a NSString.

NSString* content = [NSString stringWithContentsOfFile:path
                                              encoding:NSUTF8StringEncoding
                                                 error:NULL];