Encoding tuples as rows

In a previous post, we’ve seen how to encode collections as CSV rows. This is useful when dealing with homogeneous data, but not so much when not all cells in a given row are of the same time. One way of dealing with such situation is tuples.

Let’s imagine that we have data composed of an Int, a Float and a Boolean, and that we need to turn that into a CSV file.

The first step is to retrieve a CsvWriter instance on the desired file:

import kantan.csv._
import kantan.csv.ops._

// File in which we'll be writing the CSV data.
val out = java.io.File.createTempFile("kantan.csv", "csv")

val writer = out.asCsvWriter[(Int, Float, Boolean)](rfc.withHeader("Column 1", "Column 2", "Column 3"))

Note the type parameter to asCsvWriter: this is what the returned instance of CsvWriter will know to encode. We’re trying to write instances of (Int, Float, Boolean), which is what we passed.

The value parameters are the column separator and optional header row.

Now that we have a CsvWriter that knows how to encode (Int, Float, Boolean), we can just call its write method repeatedly:

writer.write((0, 1F, false))
writer.write((3, 4F, true))
writer.close()

Note that CsvWriter supports a fluent style of chaining operations (or, in less pretentious english, each write returns the CsvWriter itself), which I could have used to simplify the above code. I feel that spelling things out helps, though, especially the explicit call to close at the end.

Let’s make sure that we got the expected output:

scala.io.Source.fromFile(out).mkString
// res3: String = """Column 1,Column 2,Column 3
// 0,1.0,false
// 3,4.0,true
// """

What to read next

If you want to learn more about: