title: Simplest way to throw an error/exception with a custom message in Swift?
body: <p>I want to do something in Swift that I'm used to doing in multiple other languages:  throw a runtime exception with a custom message.  For example (in Java):</p>
  <pre><code>throw new RuntimeException(&quot;A custom message here&quot;)
  </code></pre>
  <p>I understand that I can throw enum types that conform to the ErrorType protocol, but I don't want to have to define enums for every type of error I throw.  Ideally, I'd like to be able mimic the example above as closely as possible.  I looked into creating a custom class that implements the <a href="https://developer.apple.com/library/prerelease/ios/documentation/Swift/Reference/Swift_ErrorType_Protocol/index.html" rel="noreferrer">ErrorType protocol</a>, but I can't even figure out that what that protocol requires.  Ideas?</p>