Question

我是scala的新手，我正在尝试重构下面的代码。我想消除下面代码中使用的“index”并循环遍历数组以获取数据。

 subgroupMetricIndividual.instances.foreach { instanceIndividual =>
   val MetricContextListBuffer: ListBuffer[Context] = ListBuffer()
   var index = 0
   contextListBufferForSubGroup.foreach { contextIndividual =>
        MetricContextListBuffer += Context(
                 entity = contextIndividual,
                 value = instanceIndividual(index).toString
        )
        index += 1
   }
}

例如，如果变量的值如下：

contextListBufferForSubGroup = ("context1","context2")
subgroupMetricIndividual.instances = {{"Inst1","Inst2",1},{"Inst3","Inst4",2}}

那么Context应该是这样的：

  { 
   entity: "context1",
   value:  "Inst1"
   },
   { 
   entity: "context2",
   value:  "Inst2"
   },
   { 
   entity: "context1",
   value:  "Inst3"
   },
   { 
   entity: "context2",
   value:  "Inst4"
   }

注意：

instanceIndividual可以拥有比contextListBufferForSubGroup中更多的元素。在这种情况下，我们必须忽略instanceIndividual中的最后一个额外元素

Answer 1

您可以将两个列表压缩为元组列表，然后将其映射到该列表。 e.g。

subgroupMetricIndividual.instances.foreach { instanceIndividual =>
  val MetricContextListBuffer = contextListBufferForSubGroup.zip(instanceIndividual).map {
    case (contextIndividual, instanceIndividualIndex) => Context(
      entity = contextIndividual,
      value = instanceIndividualIndex.toString
    )
  }
}

如果Context可以像函数Context(contextIndividual, instanceIndividualIndex.toString)一样被调用，那么你可以写得更短。

subgroupMetricIndividual.instances.foreach { instanceIndividual =>
  val MetricContextListBuffer = contextListBufferForSubGroup
    .zip(instanceIndividual.map(_.toString)).map(Context.tupled)
}

Answer 2

在不知道您的确切数据类型的情况下，我嘲笑了一些可能与您想要的内容相近的东西，并且使用地图和不可变集合稍微更具功能性

case class Context(entity:String, value:String)

val contextListBufferForSubGroup = List("context1","context2")
val subgroupMetricIndividualInstances = List(List("Inst1","Inst2",1),List("Inst3","Inst4",2))

val result: List[Context] = subgroupMetricIndividualInstances.map { instanceIndividual =>
contextListBufferForSubGroup.zip(instanceIndividual) map { case v: (String, String) =>
    Context(
      entity = v._1,
      value = v._2
    )
  }
}.flatten

在scala中循环数组的最佳方法是什么

2 个答案: