ratpack-map-and-flatmap.groovy

/**
 * The `Promise#map` method is used to retrieve
 * a value asynchronously (via a `Promise`) and
 * transform it synchronous to a new value.
 */
class MappingSpec extends Specification {

  @AutoCleanup
  ExecHarness harness = ExecHarness.harness()

  Promise<Integer> getInteger() {
    Promise.sync {
      return 1
    }
  }

  Promise<Integer> makeNumber() {
    getInteger().map { i ->
      i + 2
    }
  }

  void "should map value of promise to new value"() {
    when:
    def result = harness.yieldSingle {
      makeNumber()
    }.value

    then:
    result == 3
  }
}

/**
 * The `Promise#flatMap` method is used to retrieve
 * a value asynchronously (via a `Promise`) and
 * transform it asynchronously (via another `Promise`)
 * to a new value
 *
 */
class FlatMappingSpec extends Specification {
  
  @AutoCleanup
  ExecHarness harness = ExecHarness.harness()

  Promise<Integer> getFirstInteger() {
    Promise.sync {
      return 1
    }
  }

  Promise<Integer> getSecondNumber() {
    Promise.sync {
      return 2
    }
  }

  Promise<Integer> makeNumber() {
    getFirstInteger().flatMap { i ->
      getSecondInteger().map { x ->
        return i + x
      }
    }
  }

  void "should map value of two promises to new value"() {
    when:
    def result = harness.yieldSingle {
      makeNumber()
    }.value

    then:
    result == 3
  }
}