title: Swift Programming: getter/setter in stored property
body: <p>How do I overwrite the setter of stored property in Swift?</p>
  
  <p>In Obj-C, I can overwrite its setter, but Swift doesn't seem to be happy about getter/setters being used for stored property.</p>
  
  <p>Say I have a <code>Card</code> class with a property called <code>rank</code>. I don't want the client to give it any invalid value, therefore, in objective-C, I can overwrite <code>setRank</code> so that it performs additional check. But <code>willSet</code> in Swift doesn't seem to help because <code>newValue</code> is constant and it makes no sense to assign <code>rank</code> because setter will be called in a loop.</p>