title: What are hidden dependencies?
body: <p>Could someone please give me an example of a hidden dependency. I've googled it, and found results like this: </p>
  
  <blockquote>
    <p>"A visible dependency is a dependency that developers can see from a
    class's interface. If a dependency cannot be seen from the class's
    interface, it is a hidden dependency."</p>
  </blockquote>
  
  <p><sub>(Source - <a href="http://tutorials.jenkov.com/ood/understanding-dependencies.html#visiblehidden" rel="noreferrer">http://tutorials.jenkov.com/ood/understanding-dependencies.html#visiblehidden</a>)</sub></p>
  
  <p>But I still don't quite get it. </p>
  
  <p>Does it mean when a dependency is happening inside a function, and not a declared variable in the beginning of a class? Or is it when you simply create functions other than the signature methods declared in an interface?</p>