从类实例访问伴随对象的属性

Question

What I would like to do is create an instance of a class which has a companion object, and be able to access the static fields in the companion object from the instance of the class.

class Person(name: String, age: Integer)
{
    def getAge(): Integer = { age }
    def getName(): String = { name }
}

object Person
{
    def create(name: String, age: Integer)
    {
        new Person(name, age)
    }

    val species = "homoSapiens"
}

object mainMethod
{
    def main(args: Array[String]): Unit =
    {
        // this is what I want to make work
        val person = Person.create("Sarah", 18)
        println(person.species)
    }
}

I understand that with the current setup the species property will not be found when referencing the class instance. My question is, is it possible to manipulate the code above in some way in order to make this work?

Answer 1

This is how you can do that:

class Person(name: String, age: Int) {
  def getAge: Integer = {
    age
  }

  def getName: String = {
    name
  }

  def species: String = Person.species
}

object Person {
  def apply(name: String, age: Int): Person = new Person(name, age)

  def species = "homoSapiens"
}

object Solution extends App {
  val person = Person("sarah", 18)

  println(person.species)
}

Answer 2

If you really wanna have it via property, there is one of the weird way:

class Person(name: String, age: Integer) {
  def getAge(): Integer = { age }
  def getName(): String = { name }
}

trait PersonProps {
  val species = "homoSapiens"
}

object Person {
  def create(name: String, age: Integer) = {
    new Person(name, age) with PersonProps
  }
}