Question

我试图在Scala中构建Vector [Map [String，Any]]。我知道Vector是不可变的，我使用可变Map。

当我尝试这样做时：

def calculate_objectives(pop: Vector[Map[String, Any]]): Unit ={
  for (i <- 0 until pop_size){
    pop(i) = pop(i) + ("weights" -> decode(pop(i)("genome").asInstanceOf[Vector[Int]]))
    pop(i) = pop(i) + ("objective" -> Vector(objective1(pop(i)("weights").asInstanceOf[Vector[Float]]), objective2(pop(i)("weights").asInstanceOf[Vector[Float]])))
  }
}

我没有尝试更改Vector，只是Vector中的Map。这可能吗？

当我尝试编译此代码时，我得到两个相同的错误，我想知道这是否是问题。

Error:(102, 7) value update is not a member of Vector[scala.collection.mutable.Map[String,Any]]
  pop(i) = pop(i) + ("weights" -> decode(pop(i)("genome").asInstanceOf[Vector[Int]]))

Answer 1

Map类型为defined in Predef as scala.collection.immutable.Map。

如果你想要一个带有可变地图的矢量，那么你必须明确地将该类型声明为collection.mutable.Map，然后你必须update地图，而不是矢量：

import scala.collection.mutable.{Map => MutMap}

def calculate_objectives(pop: Vector[MutMap[String, Any]]): Unit = {
  for (i <- 0 until pop.size){
    pop(i)("weights") = decode(pop(i)("genome").asInstanceOf[Vector[Int]])
    pop(i)("objective") = Vector(
      objective1(pop(i)("weights").asInstanceOf[Vector[Float]]), 
      objective2(pop(i)("weights").asInstanceOf[Vector[Float]])
    )
  }
}

我在这里使用重命名导入将collection.mutable.Map重命名为MutMap。如果需要，您可以在collection.mutable.Map类型中写出完全限定名称pop。

Scala - 更新不可变Vector中的可变映射

1 个答案: