Hi guys,

I’m trying to build something similar to Twitter where users can follow other users. I’m not sure exactly how to properly create self-referencing schema in this case.

Migrations:

defmodule MyApp.Repo.Migrations.CreateUsers do
  use Ecto.Migration

  def change do
    create table(:users) do
      add :username, :string
    end
  end
end

defmodule MyApp.Repo.Migrations.CreateFollows do
  use Ecto.Migration

  def change do
    create table(:followings) do
      add :follower_id, references(:users, on_delete: :delete_all)
      add :followed_id, references(:users, on_delete: :delete_all)
      timestamps()
    end

    create index(:followings, [:follower_id, :followed_id], unique: true)
  end
end

Schemas:

defmodule MyApp.User do
  use Ecto.Schema

  schema "users" do
    field :username, :string

    ...
  end
end

defmodule MyApp.Follow do
  use Ecto.Schema

  schema "followings" do
    ---
  end
end

Can someone help me write the schemas properly using many_to_many please?