ios - How to use .isempty in OS X swift -

i new swift, , i'm trying make login program mac os x. know swift programming on ios, don't know os x swift. wrote program os x. finished it, need know how check whether text fields empty or not. in ios, can using .isempty property. doesn’t work on os x though. how can this?

class insideviewcontroller: nsviewcontroller {      @iboutlet var usernametext: nstextfield!     @iboutlet var passwordtext: nssecuretextfield!     @iboutlet var conformpasswordtext: nssecuretextfield!       override func viewdidload() {         super.viewdidload()          // additional setup after loading view.     }      override var representedobject: anyobject? {         didset {             // update view, if loaded.         }     }      @ibaction func signupbutton(sender: nsbutton) {         let username = usernametext.stringvalue         let userpassword = passwordtext.stringvalue         let userpasswordcon = conformpasswordtext.stringvalue          nsuserdefaults.standarduserdefaults().setobject(username, forkey: "username")         nsuserdefaults.standarduserdefaults().setobject(userpassword, forkey: "userpassword")         nsuserdefaults.standarduserdefaults().synchronize()          if (usernametext.isempty)     }  } 

if usernametext.stringvalue == "" {     //action } 

as seen here can access text of nstextfield using stringvalue property, can used modify text.