ios - How to fetch a list of items in a column from Parse cloud using swift -

i beginner ios swift , presently working parse cloud. need fetch contents of complete column list class named "student". looking print list of roll numbers student class.

my current code this:

  @ibaction func btn_download(sender: anyobject) {          var compquery = pfquery(classname:"student")         compquery.wherekey("roll", equalto:enter_rollnumber.text)          compquery.findobjectsinbackgroundwithblock {             (student: [anyobject]!, error: nserror!) -> void in             if error == nil {                 // found objects                 competition in student {                     println(competition["name"] string)                 self.display_name.text = competition["name"] string?                 }             } else {                 // log details of failure                println("error")             }         }}