title: Adding a computed observable via the prototype to a constructor function
body: <p>I'm using Knockout.js 2.0 and I'm trying to extend the prototype of the constructor function I've created by adding a computed observable but its throwing up "self.IsSubDomain is not a function". How do I solve this error? Is there another way to extend a constructor function to solve this?</p>
  
  <p><a href="http://jsfiddle.net/StrandedPirate/J44S4/3/" rel="noreferrer">http://jsfiddle.net/StrandedPirate/J44S4/3/</a></p>
  
  <p>Note: I know I could define the computed observable inside the constructor function's closure but I'm building an automated code generator for knockout view models and I need to be able to extend my objects through the prototype property.</p>