title: Swift: Does not conform to protocol NSCoding
body: <p>I am trying to use the NSCoding protocol on a class I have written in swift, but cannot seem to figure out why the compiler complains that it "does not conform to protocol NSCoding" when I do implement the required methods:</p>
  
  <pre><code>class ServerInfo: NSObject, NSCoding {
  
      var username = ""
      var password = ""
      var domain = ""
      var location = ""
      var serverFQDN = ""
      var serverID = ""
  
      override init() {
  
      }
  
      init(coder aDecoder: NSCoder!) {
          self.username = aDecoder.decodeObjectForKey("username") as NSString
          self.password = aDecoder.decodeObjectForKey("password") as NSString
          self.domain = aDecoder.decodeObjectForKey("domain") as NSString
          self.location = aDecoder.decodeObjectForKey("location") as NSString
          self.serverFQDN = aDecoder.decodeObjectForKey("serverFQDN") as NSString
          self.serverID = aDecoder.decodeObjectForKey("serverID") as NSString
      }
  
  
      func encodeWithCoder(_aCoder: NSCoder!) {
          _aCoder.encodeObject(self.username, forKey: "username")
          _aCoder.encodeObject(self.password, forKey: "password")
          _aCoder.encodeObject(self.domain, forKey: "domain")
          _aCoder.encodeObject(self.location, forKey: "location")
          _aCoder.encodeObject(self.serverFQDN, forKey: "serverFQDN")
          _aCoder.encodeObject(self.serverID, forKey: "serverID")
      }
  
  }
  </code></pre>
  
  <p>Is this a bug or am I just missing something?</p>