net.ceedubs.ficus.readers.ValueReader.scala Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of ficus_2.10 Show documentation

A Scala-friendly wrapper companion for Typesafe config

The newest version!

package net.ceedubs.ficus.readers

import com.typesafe.config.Config

/** Reads a value of type A that is located at a provided `path` in a Config. */
trait ValueReader[A] { self =>

  /** Reads the value at the path `path` in the Config */
  def read(config: Config, path: String): A

  /**
   * Turns a ValueReader[A] into a ValueReader[B] by applying the provided transformation `f` on the item of type A
   * that is read from config
   */
  def map[B](f: A => B): ValueReader[B] = new ValueReader[B] {
    def read(config: Config, path: String): B = f(self.read(config, path))
  }
}

object ValueReader {

  /** Returns the implicit ValueReader[A] in scope.
    * `ValueReader[A]` is equivalent to `implicitly[ValueReader[A]]`
    */
  def apply[A](implicit reader: ValueReader[A]): ValueReader[A] = reader

  /** ValueReader that receives a Config whose root is the path being read.
    *
    * This is generally the most concise way to implement a ValueReader that doesn't depend on the path of the value
    * being read.
    *
    * For example to read a `case class FooBar(foo: Foo, bar: Bar)`, instead of
    * {{{
    *   new ValueReader[FooBar] {
    *     def read(config: Config, path: String): FooBar = {
    *       val localizedConfig = config.getConfig(path)
    *       FooBar(
    *         foo = localizedConfig.as[Foo]("foo"),
    *         bar = localizedConfig.as[Bar]("bar"))
    *     }
    *   }
    * }}}
    * you could do
    * {{{
    * ValueReader.relative[FooBar] { config =>
    *   FooBar(
    *     foo = config.as[Foo]("foo"),
    *     bar = config.as[Bar]("bar))
    * }
    * }}}
    */
  def relative[A](f: Config => A): ValueReader[A] = new ValueReader[A] {
    def read(config: Config, path: String): A = f(config.getConfig(path))
  }
}