为什么我不能在scala中增加？

Question

  def guessing_game():Unit = {
    println("Welcome to the guessing game!!")

    val guess_count:Int = 0
    val answer = Random.nextInt(50)
    var guess_num = scala.io.StdIn.readLine("Input your guess number > ").toInt

    while(guess_num != answer || guess_count < 5){

 ====> guess_count += 1    //  <==============================

      var situation = if(guess_num > answer){"Your guess is higher!"}else{"Your guess is lower!"}
      println(situation)
      guess_num = scala.io.StdIn.readLine("Input your guess number > ").toInt
    }
    if(guess_num == answer){
      println("Congratulation....You win!!")
    }else{
      println("You hav run out of guess!")
    }

它说： 错误：（16,25）value + =不是Int的成员   表达式不会转换为赋值，因为接收器不可分配。       guess_count.toInt + = 1

Answer 1

guess_count是不可变的，（val），你无法改变它。如果您需要更改变量，请使用var。

Answer 2

你可以在scala中增加，但错误的是你正在递增并将值重新分配给最终变量，这就是为什么它会抛出错误，请更改下面的声明然后它会起作用

  

var guess_count：Int = 0

由于