在Elixir中将Ecto模型编码为JSON

Question

我正在阅读以下教程,试图了解一下elixir和phoenix:

https://robots.thoughtbot.com/testing-a-phoenix-elixir-json-api

我遇到了测试问题,主要是使用Poison.encode!在Contact模型上.我收到以下错误:

unable to encode value: {nil, "contacts"}

这导致我出现以下问题:

https://github.com/elixir-lang/ecto/issues/840 和修复:https: //coderwall.com/p/fhsehq/fix-encoding-issue-with-ecto-and-poison

我已将博客文章中的代码添加到lib/poison_encoder.ex中,但我现在收到以下错误:

no function clause matching in Poison.Encoder.Any.encode/2

我在lib/poison_encoder.ex中的代码:

defimpl Poison.Encoder, for: Any do
  def encode(%{__struct__: _} = struct, options) do
    map = struct
          |> Map.from_struct
          |> sanitize_map
    Poison.Encoder.Map.encode(map, options)
  end

  defp sanitize_map(map) do
    Map.drop(map, [:__meta__, :__struct__])
  end
end

Answer 1

更新毒药1.5.有了它,您可以在模型中声明:

@derive {Poison.Encoder, only: [:foo, :bar, :baz]}
schema "your schema" do
  field :foo
  field :bar
  field :baz
end

它会更快,更安全,更清洁.