вы можете использовать UserDefualts. например
var score = 0
//SET
UserDefaults.standard.set(score, forKey: "score")
//RETRIVE
score = UserDefaults.standard.integer(forKey: "score")
РЕДАКТИРОВАТЬ:
var currentScore = 100 //change that to the players current score.
let highScore = UserDefaults.standard.integer(forKey: "highScore") //Get the users high score from last time.
if(currentScore > highScore){// check and see if currentScore is greater than highScore.
UserDefaults.standard.set(currentScore, forKey: "highScore")//if currentScore is greater than highScore, set it in UserDefualts.
}
РЕДАКТИРОВАТЬ Pt.2
labelName.text! = "\(highScore)"