Java 8 dates and times

Java 8 comes with a better thought out dates and times API. Unfortunately, it cannot be supported as part of the core kantan.regex API - we still support Java 7. There is, however, a dedicated optional module that you can include by adding the following line to your build.sbt file:

libraryDependencies += "com.nrinaudo" %% "kantan.regex-java8" % "0.5.3"

You then need to import the corresponding package:

import kantan.regex.java8._

And this will bring GroupDecoder instances in scope for the following types:

These will use the default Java 8 formats. For example:

import kantan.regex.implicits._
import java.time._

val input = "[1978-10-12] and [2015-01-09]"

We can decode the bracketed dates without providing an explicit decoder:

input.evalRegex[LocalDate](rx"\[(\d\d\d\d-\d\d-\d\d)\]", 1).foreach(println _)
// Right(1978-10-12)
// Right(2015-01-09)

It’s also possible to provide your own format. For example, for LocalDateTime:

import java.time._
import java.time.format.DateTimeFormatter
import kantan.regex._
import kantan.regex.implicits._
import kantan.regex.java8._

implicit val decoder: GroupDecoder[LocalDate] = localDateDecoder(DateTimeFormatter.ofPattern("dd/MM/yyyy"))

val input = "[10/12/1978] and [09/01/2015]"

And we can now simply write:

input.evalRegex[LocalDate](rx"\[(\d\d/\d\d/\d\d\d\d)\]", 1).foreach(println _)
// Right(1978-12-10)
// Right(2015-01-09)

Note that while you can pass a DateTimeFormatter directly, the preferred way of dealing with pattern strings is to use the literal syntax provided by kantan.regex:

localDateDecoder(fmt"dd-MM-yyyy")

The advantage is that this is checked at compile time - invalid pattern strings will cause a compilation error:

localDateDecoder(fmt"FOOBAR")
// error: Illegal format: 'FOOBAR'
// localDateDecoder(fmt"FOOBAR")
//                  ^^^^^^^^^^^