title: Helpers in rails
body: <p>I'm just starting out in Rails and there's a lot I still need to learn so I'm likely to be on Stackoverflow more often than normal asking beginner Rails / Ruby questions.</p>
  
  <p>I'm just trying to figure out how Helpers work in Rails. From what I've seen so far, Helpers are intended to be used with Views and not so much with your Controllers.</p>
  
  <p>However I would like to make a simple function that will validate the user input given in params (check if certain params are defined and optionally check if their value is valid).  </p>
  
  <p>Can anyone explain to me what would be the best way of implementing this? (Keeping in mind that I will want to use this in many different controllers so it should be globally available.)</p>
  
  <p>I also noticed that by default Rails does not generate a lib folder in the main application folder.  Are developers to place their libs outside the app folder in the main folder, or does Rails use libraries differently?</p>