title: Change navigationController backButton title in Swift
body: <p>I am trying to change the navigation controller's back button title and couldn't do it so far.
  I am building an app that can change the UI language with a UISegmentedControl.
  I created a model, and when we change the language in the segmented control it triggers the method that makes the UI conform to the model (inside the model the language is set).
  The code works fine for everything but the backButton title. I have tried different ways of accessing it. The current one is:
  <a href="https://i.stack.imgur.com/RHWBO.png" rel="nofollow noreferrer">The way I am trying to modify it now.</a></p>
  <p>I also tried:</p>
  <pre><code>self.navigationItem.backButtonTitle = model.navigationBackButtonTitle
  </code></pre>
  <p>and</p>
  <pre><code>self.navigationItem.backBarButtonItem?.title = model.navigationBackButtonTitle
  </code></pre>
  <p>and even</p>
  <pre><code>self.navigationItem.leftBarButtonItem?.title = model.navigationBackButtonTitle
  </code></pre>
  <p>I am starting in development and trying to change careers, so forgive me if I am asking something wrong. I hope you guys can help me out.</p>
  <p>PS.: I was able to modify the back button color in another method using the code below.
  self.navigationController?.navigationItem.backBarButtonItem?.tintColor = buttonColor</p>