medium_post_schema_final.ex

defmodule BlogExample.Schema.Category do
  use Ecto.Schema

  @primary_key {:name, :string, []}

  embedded_schema do
    field(:current_popularity, :integer)
  end
end

defmodule BlogExample.Schema.Post do
  use Ecto.Schema

  schema "posts" do
    field(:title, :string, null: false)
    field(:contents, :string, null: false)

    # this is new
    belongs_to(:category, BlogExample.Schema.Category,
      foreign_key: :category_name,
      references: :name,
      type: :string
    )

    belongs_to(:user, BlogExample.Schema.User)
  end
end