scala - 从辅助构造函数初始化 val

Question

我有以下类代表一定数量的钱:

class Money(initDollars: Int, initCents: Int){

  require (initDollars >= 0 && initCents >= 0)

  private def this(positive: Boolean, initDollars: Int, initCents: Int) = {
    this(initDollars, initCents)
    //this.positive = positive
  }

  val positive: Boolean = true
  val dollars = initDollars + initCents/100
  val cents = initCents % 100
  private val totalAmount = dollars * 100 + cents

  def unary_- = new Money(!positive, dollars, cents)
}

object Money{
  def apply(initDollars: Int, initCents: Int) = new Money(initDollars, initCents)
}

金额也可以是负数，我想像这样创建它:

val am = -Money(1, 20)

所以我想初始化 val positive来自二级构造函数，但我不能这样做，因为它重新分配给 val。我也加不了 val在二级构造函数的参数列表中。有人可以帮忙吗？

Answer 1

反过来做。

class Money private (pos: Boolean, initDollars: Int, initCents: Int) {

  require (initDollars >= 0 && initCents >= 0)

  def this(initDollars: Int, initCents: Int) = {
    this(true, initDollars, initCents)
  }

  val positive: Boolean = pos
  val dollars = initDollars + initCents/100
  val cents = initCents % 100
  private val totalAmount = dollars * 100 + cents

  def unary_- = new Money(!positive, dollars, cents)
}