// While fetching NSDocumentDirectory Path it will give in the array format. So instead of giving NSString you need to give NSArray.. check below code
// Try this
NSArray * aDocumentsDirectory = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docPath = [aDocumentsDirectory objectAtIndex:0];
NSString *finaldocPath = [docPath stringByAppendingPathComponent:fileName];