CustomizedFunction3.scala

package org.snippets
import scala.concurrent.{Future, Promise}

class Test {

  def test(): Function3[String, String, String, String] = {
    new Function3[String, String, String, String] {
      @throws(classOf[Exception])
      override def apply(arg1: String, arg2: String, arg3: String): Future[String] = {
        Promise[String]().future
      }
    }
  }

  def test1(): Function3[String, String, String, String] = { (a: String, b: String, c: String) =>
    Promise[String]().future
  }
}

trait Function3[-T1, -T2, -T3, +R] extends java.io.Serializable {
  @throws(classOf[Exception])
  def apply(arg1: T1, arg2: T2, arg3: T3): Future[R]

}

object Function3 {
  def unapply[T1, T2, T3, R](arg: Function3[T1, T2, T3, R]): Option[Function3[T1, T2, T3, R]] = Some(arg)
  implicit class ScalaFunction3IsMyFunction3y[T1, T2, T3, R](func3: (T1, T2, T3) => Future[R]) extends Function3[T1, T2, T3, R] {
    @throws(classOf[Exception])
    override def apply(arg1: T1, arg2: T2, arg3: T3) = func3.apply(arg1, arg2, arg3)
  }
}