ReferenceType.swift

class Match {
  var score: Int

  init(score: Int) {
    self.score = score
  }
}

func finish(_ match: Match) {
  match.score = 100 // Updating the score here changes the score on the original copy
}

let match = Match(score: 10)
print(match.score) // prints 10
finish(match) // passing match variable to the function
print(match.score) // prints 100