如何更新 Map 值也是 Scala 中的 Map？

Question

我正在嘗試在不可變的 Map 中更新不可變的 Map，但這給了我一個錯誤：

var m: immutable.Map[Int, immutable.Map[String, Int]] = Map[Int, immutable.Map[String, Int]]()

val item = Map[String, Int]("Test" -> 0)
m += (1, item)

val newVal: Int = m(1)("Test") + 1
val newValMap = Map[String, Int]("Test"-> newVal)
// This gives an error
m += (1, newValMap)

錯誤：

value += is not a member of scala.collection.immutable.Map[Int,scala.collection.immutable.Map[String,Int]]
  Expression does not convert to assignment because:
    type mismatch;
     found   : Int
     required: (Int, scala.collection.immutable.Map[String,Int])
    type mismatch;
     found   : (String, Int)
     required: (Int, scala.collection.immutable.Map[String,Int])
    expansion: TestClass.this.m = TestClass.this.m.+(<1: error>, "Test".$minus$greater(1))
        m += (1, ("Test" -> 1))

如何在不使m可變的情況下用m中的新值替換不可變的 Map 值？

Answer 1

正如@Luis Miguel Mejía Suárez 在評論中指出的那樣，使用updated和updatedWith方法解決了這個問題。 示例： https://scastie.scala-lang.org/BalmungSan/kdlqN3t5SGiQ26oDPyy0jg/2