Scala：将字符串数组解析为案例类 [英] Scala: Parsing Array of String to a case class

问题描述

我创建了一个这样的案例类：

I have created a case class like this:

def case_class(): Unit = {
   case class StockPrice(quarter : Byte,
                      stock : String,
                      date : String,
                      open : Double,
                      high : Double,
                      low : Double,
                      close : Double,
                      volume : Double,
                      percent_change_price : Double,
                      percent_change_volume_over_last_wk : Double,
                      previous_weeks_volume : Double,
                      next_weeks_open : Double,
                      next_weeks_close : Double,
                      percent_change_next_weeks_price : Double,
                      days_to_next_dividend : Double,
                      percent_return_next_dividend : Double
                     )

我有像这样的字符串数组中的数千行：

And I have thousands of line as Array of String like this:

1,AA,1/7/2011,$15.82,$16.72,$15.78,$16.42,239655616,3.79267,,,$16.71,$15.97,-4.42849,26,0.182704

1,AA,1/14/2011,$16.71,$16.71,$15.64,$15.97,242963398,-4.42849,1.380223028,239655616,$16.19,$15.79,-2.47066,19,0.187852

1,AA,1/21/2011,$16.19,$16.38,$15.60,$15.79,138428495,-2.47066,-43.02495926,242963398,$15.87,$16.13,1.63831,12,0.189994

1,AA,1/28/2011,$15.87,$16.63,$15.82,$16.13,151379173,1.63831,9.355500109,138428495,$16.18,$17.14,5.93325,5,0.185989

如何将Array中的数据解析为该case类？
谢谢您的帮助！

How Can I parse data from Array into that case class? Thank you for your help!

推荐答案

您可以按照以下步骤进行操作（我以简化示例为例）

You can proceed as below (I've taken simplified example)

给出您的案例类别和数据（行）

Given your case class and data (lines)

// Your case-class
case class MyCaseClass(
  fieldByte: Byte,
  fieldString: String,
  fieldDouble: Double
)

// input data
val lines: List[String] = List(
  "1,AA,$1.1",
  "2,BB,$2.2",
  "3,CC,$3.3"
)

---

注意：您可以从文本文件 as

val lines = Source.fromFile("my_file.txt").getLines.toList

---

您可以使用一些实用的映射方法（清理和放大） ;解析）

---

You can have some utility methods for mapping (cleaning & parsing)

// remove '$' symbols from string
def removeDollars(line: String): String = line.replaceAll("\\$", "")

// split string into tokens and
// convert into MyCaseClass object
def parseLine(line: String): MyCaseClass = {
  val tokens: Seq[String] = line.split(",")
  MyCaseClass(
    fieldByte = tokens(0).toByte,
    fieldString = tokens(1),
    fieldDouble = tokens(2).toDouble
  )
}

---

然后使用它们将字符串转换为案例类对象

---

And then use them to convert strings into case-class objects

// conversion
val myCaseClassObjects: Seq[MyCaseClass] = lines.map(removeDollars).map(parseLine)

---

作为更高级（广义）方法，您可以生成映射（解析）函数，使用 reflection 之类的东西将令牌转换为案例类的字段，如此处

---

As a more advanced (and generalized) approach, you can generate the mapping (parsing) function for converting tokens into fields of your case-class using something like reflection, as told here

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