title: How to handle environment-specific settings in your rails?
body: <p>Currently, the rails environment for my local machine development, i am getting reset password url like this 'localhost:3001/reset_password/aBRINDss'.
  i am getting localhost:3001 because i am using development env.</p>
  
  <p>currently in mailer i am using the environment like this</p>
  
  <pre><code>@reset_password_email = Settings.DEVELOPMENT_HOST_URL + '/users/reset_password/' + user.reset_password_token
  </code></pre>
  
  <p>is there any way in which i don't have to mention different HOST_URL in application.yml for each env and it takes automatically host url according to it's current environment. and i can use it here direct in <code>@reset_password_email = Settings.DEVELOPMENT_HOST_URL + '/users/reset_password/' + user.reset_password_token</code>
  in place of <strong><em>Settings.DEVELOPMENT_HOST_URL</em></strong></p>