I\'m retrieving data from Firebase Google. I\'m checking the data i received is expire or not.
func checkBought(movieName : String) -> Bool{
    var yesOrNo          
        The classic:
You cannot return anything from a method which contains an asynchronous task
You need a completion block, simply
func checkBought(movieName : String, completion:(Bool) -> Void) {
    boughtRef.observeEventType(.Value, withBlock: { (snap) in
    if snap.value![movieName]! != nil {
      if self.timestamp > snap.value![movieName]! as! Double {
        //expire
        print("expire")
        completion(false)
      } else {
        //not expire
        print("not expire")
        completion(true)
      }
    } else {
      //not bought yet
      print("No movie")
      completion(false)
    }
  })
}
Or easier
func checkBought(movieName : String, completion:(Bool) -> Void) {
  boughtRef.observeEventType(.Value, withBlock: { (snap) in
    if let movieStamp = snap.value![movieName] as? Double where self.timestamp <= movieStamp {
      //not expire
      print("not expire")
      completion(true)
    } else {
      // expire or not bought yet
      print("expire or no movie")
      completion(false)
    }
  })
}
And call it with
checkBought("Foo") { flag in
   print(flag)
}