elixir - 如何在 Ecto 模型中使用 uuid

Question

我正在尝试将 uuid 与 ecto 一起使用。我可以查询所有内容，但我在 Repo.get 中遇到了 unable to encode value 错误。

defmodule Rocket.Model do
  defmacro __using__(_) do
    quote do
      use Ecto.Model
      @primary_key {:id, :uuid, []}
      @foreign_key_type :uuid
    end
  end
end

defmodule Rocket.User do
  use Rocket.Model

  schema "users" do
    field :created_at, :datetime
    field :name, :string
    field :email, :string
    field :password, :string
    field :timezone, :string
  end
end


iex(37)> Rocket.Repo.get(Rocket.User,"00000000-0000-0000-0000-00000000011b") 
21:51:58.291 [debug] SELECT u0."id", u0."created_at", u0."name", u0."email", u0."password", u0."timezone" FROM "users" AS u0 WHERE (u0."id" = $1) (0.4ms)
** (Postgrex.Error) unable to encode value `"00000000-0000-0000-0000-00000000011b"` as type uuid
      (ecto) lib/ecto/adapters/sql/worker.ex:18: Ecto.Adapters.SQL.Worker.query!/4
      (ecto) lib/ecto/adapters/sql.ex:186: Ecto.Adapters.SQL.use_worker/3
    (rocket) web/models/repo.ex:2: Rocket.Repo.log/2
      (ecto) lib/ecto/adapters/sql.ex:315: Ecto.Adapters.SQL.all/5
      (ecto) lib/ecto/repo/queryable.ex:20: Ecto.Repo.Queryable.all/4
      (ecto) lib/ecto/repo/queryable.ex:43: Ecto.Repo.Queryable.one/4
iex(37)> 

使用所有功能，但 uuid 在控制台或 json 解码中均未表示为字符串:

iex(38)> user = Rocket.Repo.all(Rocket.User) |> List.first
21:58:55.450 [debug] SELECT u0."id", u0."created_at", u0."name", u0."email", u0."password", u0."timezone" FROM "users" AS u0 (1.5ms)
%Rocket.User{created_at: %Ecto.DateTime{day: 3, hour: 2, min: 16, month: 1,
  sec: 3, year: 2015}, email: "joel@foo.com",
 id: <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 29>>, name: "Joel",
 password: "$1$E0eFWgDt$YgQTEByVT7prYkT2IqBjL1", timezone: nil}
iex(39)> IO.puts Poison.Encoder.encode(udb,[])  
{"timezone":null,"password":"$1$E0eFWgDt$YgQTEByVT7prYkT2IqBjL1","name":"Joel","id":"\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0001\u001D","email":"joel@foo.com","created_at":{"year":2015,"sec":3,"month":1,"min":16,"hour":2,"day":3}}
:ok

Answer 1

UUID 只有 16 个字节，所以你从 all/1 得到的实际上是正确的。如果您想使用 UUID 的详细表示，您可以显式转换它或使用自定义类型在将数据加载和转储到数据库时自动为您完成工作。我已经谈到了自定义类型 in this answer .