Awesome

CSVSide

CSV readers and combinators for Scala. Made with Cats.

Copyright 2015 Richard Dallaway and Dave Gurnell. Licensed Apache 2.

Getting Started

Grab the code from Bintray by adding the following to your build.sbt:

scalaVersion := "2.11.7"

resolvers += "Awesome Utilities" at "https://dl.bintray.com/davegurnell/maven"

libraryDependencies += "io.underscore" %% "csvside" % "0.11.1"

Fixed Row Reader

Here's an example that reads directly from a String. You can also read from a java.io.File or a java.io.Reader:

// We want to parse this CSV...
val csv = """
  |Str,Bool,Int
  |abc,true,123
  |"a b",false,321
  |,,
  |abc,abc,abc
""".trim.stripMargin

// To a sequence of this data structure...
case class Test(str: String, num: Int, bool: Option[Boolean])

// We import Csvside...
import csvside._

// We define a RowFormat...
import cats.syntax.cartesian._
implicit val testFormat: RowFormat[Test] = (
  "Str".csv[String] |@|
  "Int".csv[Int] |@|
  "Bool".csv[Option[Boolean]]
).imap(Test.apply)(unlift(Test.unapply))

// We read the data...
val ans = Csv.fromString[Test](csv).toList
// ans: List[csvside.CsvValidated[Test]] = List(
//   Valid(Test(abc,123,Some(true))),
//   Valid(Test(a b,321,Some(false))),
//   Invalid(List(CsvError(4,Int,Must be a whole number))),
//   Invalid(List(CsvError(5,Int,Must be a whole number),
//                CsvError(5,Bool,Must be a yes/no value or blank))))

// And we write it back to CSV...
import cats.data.Validated
val validOnly = ans collect { case Validated.Valid(test) => test }
val finalCsv = Csv.toString(validOnly)
// finalCsv: String =
// ""Str","Int","Bool"
// "abc","123","true"
// "a b","321","false"
// "

Row Reader Depends on Header Row

If the format of the rows depends on the values in the header row, we can use a ListReader[A] to generate a ColumnReader[A] on the fly:

// We want to parse the cells in this CSV...
val csv = s"""
  |Row,Col1,Col2,Col3
  |x,1,2,3
  |y,,,
  |z,3,,1
""".trim.stripMargin

// To a sequence of this data structure...
case class Test(key: String, values: Map[CsvPath, Option[Int]])

// We do this by creating a `ListReader` that
// parses the column headings and creates a `ColumnReader`
// to read the rest of the file.

// We import from Csvside...
import csvside._

// We define a ListReader...
import cats.data.Validated.{valid, invalid}
import cats.syntax.cartesian._
import cats.syntax.validated._
implicit val testReader: ListReader[Test] =
  ListReader[Test] {
    case head :: tail =>
      (head.read[String] |@| tail.readMap[Option[Int]]).map(Test.apply).valid

    case Nil =>
      invalid(List(CsvError(1, "", "File must contain at least one column")))
  }

// And we read the data...
val ans = Csv.fromString[Test](csv).toList
// ans: List[CsvValidated[Test]] =
//   List(
//     Valid(Test("x", Map("Col1" -> Some(1), "Col2" -> Some(2), "Col3" -> Some(3)))),
//     Valid(Test("y", Map("Col1" -> None,    "Col2" -> None,    "Col3" -> None))),
//     Valid(Test("z", Map("Col1" -> Some(3), "Col2" -> None,    "Col3" -> Some(1)))))