test/oop_test.exs

defmodule OOPTest do
  use ExUnit.Case
  import OOP

  test "define empty class" do
    c = class Person do
    end

    assert c
    purge Person
  end

  test "instantiate empty object" do
    class Person do
    end

    alice = Person.new
    assert alice.class == Person
    purge Person
  end

  test "define methods on objects" do
    class Person do
      def zero do
        0
      end

      def sum1(a) do
        a
      end

      def sum2(a, b) do
        a + b
      end
    end

    alice = Person.new
    assert alice.zero() == 0
    assert alice.sum1(1) == 1
    assert alice.sum2(1, 2) == 3
    purge Person
  end

  test "define fields" do
    class Person do
      var :name

      def title(prefix) do
        "#{prefix} #{this.name}"
      end
    end

    alice = Person.new
    assert alice.name == nil

    bob = Person.new(name: "Bob")
    assert bob.name == "Bob"
    bob.set_name("Hipster Bob")
    assert bob.name == "Hipster Bob"
    assert bob.title("Mr.") == "Mr. Hipster Bob"

    assert alice.name == nil

    purge Person
  end

  test "define private fields" do
    class AppleInc do
      private_var :registered_devices

      def registered_devices_count do
        length(this.registered_devices)
      end
    end

    apple = AppleInc.new(registered_devices: ["Alice's iPhone", "Bob's iPhone"])

    assert_raise RuntimeError, "Cannot access private var registered_devices", fn ->
      apple.registered_devices
    end

    assert apple.registered_devices_count == 2

    purge AppleInc
  end

  test "define friend class" do
    class NSA do
      def get_data(company) do
        company.registered_devices
      end
    end

    class Thief do
      def get_data(company) do
        company.registered_devices
      end
    end

    class AppleInc do
      friend NSA
      private_var :registered_devices
    end

    apple = AppleInc.new(registered_devices: ["Alice's iPhone", "Bob's iPhone"])
    thief = Thief.new
    nsa = NSA.new

    assert_raise RuntimeError, "Cannot access private var registered_devices", fn ->
      thief.get_data(apple)
    end

    assert nsa.get_data(apple) == ["Alice's iPhone", "Bob's iPhone"]

    purge [AppleInc, Thief, NSA]
  end

  test "inheritance" do
    class Animal do
      var :name

      def title(prefix) do
        "#{prefix} #{this.name}"
      end
    end

    class Dog < Animal do
      var :breed
    end

    snuffles = Dog.new(name: "Snuffles", breed: "Shih Tzu")
    assert snuffles.name == "Snuffles"
    assert snuffles.breed == "Shih Tzu"
    assert snuffles.title("Mr.") == "Mr. Snuffles"

    purge [Animal, Dog]
  end

  test "multiple inheritance" do
    class Human do
      var :name
    end

    class Horse do
      var :horseshoes_on?
    end

    class Centaur < [Human, Horse] do
    end

    john = Centaur.new(name: "John", horseshoes_on?: true)
    assert john.name == "John"
    assert john.horseshoes_on? == true

    purge [Human, Horse, Centaur]
  end

  test "define abstract class" do
    abstract class ActiveRecord.Base do
    end

    assert_raise RuntimeError, "cannot instantiate abstract class #{ActiveRecord.Base}", fn ->
      ActiveRecord.Base.new
    end

    class Post < ActiveRecord.Base do
      var :title
    end

    assert Post.new(title: "Post 1").title == "Post 1"
    purge [ActiveRecord.Base, Post]
  end

  test "abstract class inheriting from abstract class" do
    abstract class ActiveRecord.Base do
    end

    abstract class ApplicationRecord < ActiveRecord.Base do
    end

    assert_raise RuntimeError, "cannot instantiate abstract class #{ActiveRecord.Base}", fn ->
      ActiveRecord.Base.new
    end

    assert_raise RuntimeError, "cannot instantiate abstract class #{ApplicationRecord}", fn ->
      ApplicationRecord.new
    end

    class Post < ApplicationRecord do
      var :title
    end

    assert Post.new(title: "Post 1").title == "Post 1"
    purge [ActiveRecord.Base, ApplicationRecord, Post]
  end

  test "define final class" do
    final class FriezaFourthForm do
    end

    assert FriezaFourthForm.new

    assert_raise RuntimeError, "cannot subclass final class #{FriezaFourthForm}", fn ->
      class FriezaFifthForm < FriezaFourthForm do
      end
    end

    purge [FriezaFourthForm, FriezaFifthForm]
  end

  defp purge(module) when is_atom(module) do
    :code.delete(module)
    :code.purge(module)
  end
  defp purge(modules) when is_list(modules) do
    Enum.each(modules, &purge/1)
  end
end