elixirphoenix-frameworkelixir-poison

Poison.EncodeError at GET /api unable to encode value: {nil, "paths"}

When attempting to render json data I get the following error in my controller.

Poison.EncodeError at GET /api
unable to encode value: {nil, "paths"}

web/controllers/api_controller.ex:1 App.ApiController.action/2

After searching around I attempted to my model like this:

defmodule App.Api do
  use App.Web, :model

  @derive {Poison.Encoder, only: [:basePath, :definitions, :paths]}
  schema "apis" do
    field :basePath, :string
    field :definitions, :string
    has_many :paths, App.Path

    timestamps()
  end
end

Which doesn't seem to resolve the error. I got this error after attempting to preload my paths field in my controller like this:

defmodule App.ApiController do
  use App.Web, :controller

  alias App.Api

  def index(conn, _params) do
    apis = Repo.all(Api) |> Repo.preload(:paths)
    render conn, "index.json", apis: apis
  end
end

I'm able to insert data find into my database and I can query it all with:

Repo.all(Api) |> Repo.preload(:paths)

Any thoughts on what else to try? Thanks

Solution

  • If you want to preload your :paths, you should use derive on Documentr2.Path module too.

    @derive [Poison.Encoder]

    or

    @derive {Poison.Encoder, only: [:field_you_want]}