Elixir phoenix - Render Ecto schema to json with relationships

  defmodule MyApp.UserView do      use JsonView      def render("user.json", %{user: user}) do        render_json(user, [:first_name, :last_name, :vatar], [], [])      end  end  defmodule MyApp.PostView do      use JsonView      # define which fields return without modifying      @fields [:title, :content, :excerpt, :cover]      # define which fields that need to format or calculate, you have to define `render_field/2` below      @custom_fields [:like_count]      # define which view used to render relationship      @relationships [author: MyApp.UserView]      def render("post.json", %{post: post}) do          # 1st way if `use JsonView`          render_json(post, @fields, @custom_fields, @relationships)      end      def render_field(:like_count, item) do          # load like_count from some where      end  end

post = %Post{    title: "Hello JsonView",    excerpt: "Now you can render Json easier",    content: "Install and put it to work",    cover: nil,    inserted_at: ~N[2021-07-05 00:00:00],    updated_at: ~N[2021-07-09 00:00:00],    author: %User{        first_name: "Daniel",        last_name: "James",        email: "[email protected]",        avatar: nil,        inserted_at: ~N[2021-06-30 00:00:00]        updated_at: ~N[2021-07-02 00:00:00]    }}MyApp.PostView.render("post.json", %{post: post})# or invoke from PostControllerrender(conn, "post.json", post: post)

%{    title: "Hello JsonView",    excerpt: "Now you can render Json easier",    content: "Install and put it to work",    cover: nil,  like_count: nil,    author: %{        first_name: "Daniel",        last_name: "James"    }}