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Fix CSV writing example #2

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Oct 29, 2023
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Fix CSV writing example #2

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51 changes: 30 additions & 21 deletions docs/examples.md
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Original file line number Diff line number Diff line change
Expand Up @@ -430,10 +430,9 @@ If you want to save a list of a case class into a CSV file this helper method ma
```scala mdoc:reset:silent
//> using lib "org.typelevel::toolkit::@VERSION@"

import fs2.io.file.Files
import fs2.data.csv.*
import fs2.data.csv.generic.semiauto.*
import fs2.io.file.Path
import fs2.io.file.{Files, Path}
import cats.effect.{IO, IOApp}
import fs2.{Pipe, Stream}

Expand Down Expand Up @@ -468,39 +467,48 @@ object WriteBooksToCsv extends IOApp.Simple:
.emits(input)
.through(writeCaseClassToCsv(Path("books.csv")))
.compile
.drain *> IO.println("Finished writing books to books.csv.")```
.drain *> IO.println("Finished writing books to books.csv.")
```

@:choice(scala-2)

```scala mdoc:reset:silent
//> using lib "org.typelevel::toolkit::@VERSION@"

import fs2.io.file.Files
import fs2.data.csv.*
import fs2.data.csv.generic.semiauto.*
import fs2.io.file.Path
import fs2.data.csv._
import fs2.data.csv.generic.semiauto._
import fs2.io.file.{Files, Path}
import cats.effect.{IO, IOApp}
import fs2.{Pipe, Stream}

/** Define your case class and derive an encoder for it */
case class YourCaseClass(n: String, i: Int)
implicit val csvRowEncoder: CsvRowEncoder[YourCaseClass, String] = deriveCsvRowEncoder
object YourCaseClass {
implicit val csvRowEncoder: CsvRowEncoder[YourCaseClass, String] =
deriveCsvRowEncoder
}

/** This is our helper function that writes a case class as a csv given a path. */
def writeCaseClassToCsv[A](
path: Path
)(using CsvRowEncoder[A, String]): Pipe[IO, A, Nothing] =
_.through(encodeUsingFirstHeaders(fullRows = true))
.through(fs2.text.utf8.encode)
.through(Files[IO].writeAll(path))
.drain
object Helpers {

/** Let's imagine we have a `Book` case class we would like to write to
* a .csv file.
/** This is our helper function that writes a case class as a csv given a
* path.
*/
def writeCaseClassToCsv[A](
path: Path
)(implicit encoder: CsvRowEncoder[A, String]): Pipe[IO, A, Nothing] =
_.through(encodeUsingFirstHeaders(fullRows = true))
.through(fs2.text.utf8.encode)
.through(Files[IO].writeAll(path))
.drain

}

/** Let's imagine we have a `Book` case class we would like to write to a .csv
* file.
*/
object WriteBooksToCsv extends IOApp.Simple:
object WriteBooksToCsv extends IOApp.Simple {
case class Book(id: Long, name: String, isbn: String)
implicit val csvRowEncoder: [Book, String] = deriveCsvRowEncoder
implicit val csvRowEncoder: CsvRowEncoder[Book, String] = deriveCsvRowEncoder

val input = Seq(
Book(1, "Programming in Scala", "9780997148008"),
Expand All @@ -511,9 +519,10 @@ object WriteBooksToCsv extends IOApp.Simple:
def run: IO[Unit] =
Stream
.emits(input)
.through(writeCaseClassToCsv(Path("books.csv")))
.through(Helpers.writeCaseClassToCsv(Path("books.csv")))
.compile
.drain *> IO.println("Finished writing books to books.csv.")
}
```

@:@
Expand Down