title: Getting "use of undeclared type 'NoError'" with ReactiveCocoa
body: <p>I am trying to learn ReactiveCocoa and have a hard time getting started. I keep hitting minor bumps as API and tutorials seems to be outdated quickly. Maybe I have the wrong impression.</p>
  
  <p>Just trying to follow <a href="http://blog.scottlogic.com/2015/04/28/reactive-cocoa-3-continued.html">this</a> I do not seem to have <code>NoError</code>.</p>
  
  <p><a href="https://i.stack.imgur.com/RLaHO.png"><img src="https://i.stack.imgur.com/RLaHO.png" alt="enter image description here"></a></p>
  
  <p>It should be imported correctly, since I have access to <code>Signal</code>, <code>rac_textSignal</code> etc. but I don't know why NoError is not available.</p>
  
  <p>Their <a href="https://github.com/ReactiveCocoa/ReactiveCocoa/blob/master/Documentation/DesignGuidelines.md#failures-behave-like-exceptions-and-propagate-immediately">documentation</a> mentions <code>NoError</code> as well but that leads to a <a href="https://github.com/ReactiveCocoa/ReactiveCocoa/blob/master/ReactiveCocoa/Swift/Errors.swift">404</a>.</p>
  
  <p>This <a href="http://spin.atomicobject.com/2015/10/26/reactivecocoa-4-differences/">transition to RAC4</a> mentions <code>NoError</code> as well. Why is <code>NoError</code> undeclared? I am using ReactiveCocoa 4.0.1.</p>
  
  <p>Edit: I just added <code>public enum NoError : ErrorType {}</code> to the top of the file and it works now. I am not sure if this is a proper solution to the problem though. It is not mentioned in guides and tutorials that I should extend <code>ErrorType</code> myself.</p>