Where to place a .txt file and read from it in a IOS project

if let path = Bundle.main.path(forResource: "README", ofType: "txt") {
  do {
    textView.text = try String(contentsOfFile: path, encoding: .utf8)
  } catch let error {
    // Handle error here
  }
}

Just drop the file anywhere into the project browser and make sure it is added to the right target.

Just to expand on the answer, you can also place them in a folder and use:
+ pathForResource:ofType:inDirectory:.