更新后的Postgrex版本的扩展行为

Question

我有这个JSON模块

defmodule EvercamMedia.Types.JSON do
  @behaviour Ecto.Type

  def type, do: :json

  def cast(term)
      when is_map(term)
        or is_binary(term)
        or is_list(term)
        or is_number(term),
    do: {:ok, term}

  def cast(_), do: :error

  def load(term), do: {:ok, term}

  def dump(term), do: {:ok, term}
end

defmodule EvercamMedia.Types.JSON.Extension do
  alias Postgrex.TypeInfo

  @behaviour Postgrex.Extension

  def init(_parameters, opts),
    do: Keyword.fetch!(opts, :library)

  def matching(_library),
    do: [type: "json", type: "jsonb"]

  def format(_library),
    do: :binary

  def encode(%TypeInfo{type: "json"}, map, _state, library),
    do: library.encode!(map)
  def encode(%TypeInfo{type: "jsonb"}, map, _state, library),
    do: <<1, library.encode!(map)::binary>>

  def decode(%TypeInfo{type: "json"}, json, _state, library),
    do: library.decode!(json)
  def decode(%TypeInfo{type: "jsonb"}, <<1, json::binary>>, _state, library),
    do: library.decode!(json)
end

我收到了很多警告

warning: undefined behaviour function decode/1 (for behaviour Postgrex.Extension)
  lib/evercam_media/json.ex:20
warning: undefined behaviour function encode/1 (for behaviour Postgrex.Extension)
  lib/evercam_media/json.ex:20
warning: undefined behaviour function init/1 (for behaviour Postgrex.Extension

我们使用它来处理JSON。我只想去掉那些警告。我知道这是过时的postgrex版本，但我只想消除这些警告。

Answer 1

定义Postgrex.Extension behaviour decode/1 (以及encode/1和init/1)所请求的内容。如果你不打算使用它，那就做：

def decode(_), do: :ok
def encode(_), do: :ok
def init(_), do: :ok

这里的问题是@behaviour声明了许多回调，这是，任何实现的契约。除非实现实现所有回调，否则Elixir编译器会发出警告。