Parse - Append data to row instead of saving new

Question

i have created a custom class "Interaction" which i want to store the buttons tapped so i can reinstate on next signing. This class has a pointer "fromUser" that points to the user objectId. i had pictured this as only having 1 row per pointer and one column for each pack (pk00, pk01) which would either record clicks in that pack as an array or just show the last click removing any previous data.

at the moment i have it creating a new row per click using the following code, but can't seem to get the data to append the row

    func writeUserHistory() {

        let fieldName = self.selectedPackName

        let interaction = PFObject(className: "Interaction")

            interaction.add(self.partArray[indexPath.item].id, forKey: fieldName)

            interaction.setObject(PFUser.current()!, forKey: "fromUser")
            interaction["fromUser"] = PFUser.current()



        PFObject.saveAll(inBackground: [interaction])

    }

    writeUserHistory()

Answer 1

You are creating a new object every time you call this method here :

 let interaction = PFObject(className: "Interaction")

Create interaction outside of your function :

let interaction = PFObject(className: "Interaction")

func writeUserHistory() {

        let fieldName = self.selectedPackName

            interaction.add(self.partArray[indexPath.item].id, forKey: fieldName)

            interaction.setObject(PFUser.current()!, forKey: "fromUser")
            interaction["fromUser"] = PFUser.current()



        PFObject.saveAll(inBackground: [interaction])

    }

writeUserHistory()