title: Abstract functions in Swift Language
body: <p>I'd like to create an abstract function in swift language. Is it possible?</p>
  
  <pre><code>class BaseClass {
      func abstractFunction() {
          // How do I force this function to be overridden?
      }
  }
  
  class SubClass : BaseClass {
      override func abstractFunction() {
          // Override
      }
  }
  </code></pre>