title: Coffeescript trouble updating instance property
body: <p>I'm having trouble accessing and updating what I <em>think</em> is an instance property in coffeescript.  I'm trying to update the @cart_total.  The first time I update the total, it works fine.  However, it only works the first time.  It seems the @cart_total is only updating once.  </p>
  
  <p>Here's the code:</p>
  
  <pre><code>class Cart 
  
    constructor: ()-&gt;
      @cart_total = 0.00 
  
  
    updateTotal: (amt)-&gt;
      @cart_total = @cart_total + amt
  
  
    this.updateTotal( @lineItem.total )
  </code></pre>
  
  <p>When I call updateTotal, it only seems to work the first time.  I am truly grateful for any help - thank you!</p>
  
  <p>EDIT : </p>
  
  <p>I call updateTotal from within the class.  I added the code above.  </p>