如何配置上传和附件库弧？

Question

我尝试使用和配置arc和arc_ecto，如其自述文件中所述。不幸的是我收到了错误。我该如何解决？

mix phoenix.new my_app --database mysql
cd my_app
mix ecto.create
mix deps.get
mix phoenix.gen.html User users name
mix arc.g avatar
mix ecto.gen.migration add_avatar_to_users

该迁移的代码：

defmodule MyApp.Repo.Migrations.AddAvatarToUsers do
  use Ecto.Migration

  def change do
    alter table :users do
      add :avatar, :string
    end
  end
end

比我运行迁移：

mix ecto.migrate

问题

我启动服务器导致错误：

$ mix ecto.server

== Compilation error on file web/controllers/user_controller.ex ==
** (CompileError) web/controllers/user_controller.ex:14: MyApp.User.__struct__/0 is undefined, cannot expand struct MyApp.User
    (elixir) src/elixir_map.erl:58: :elixir_map.translate_struct/4
    (stdlib) lists.erl:1353: :lists.mapfoldl/3
    web/controllers/user_controller.ex:13: (module)
    (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6


== Compilation error on file web/models/user.ex ==
** (CompileError) web/models/user.ex:3: module Arc.Ecto.Schema is not loaded and could not be found
    (elixir) expanding macro: Kernel.use/1
    web/models/user.ex:3: MyApp.User (module)
    (elixir) lib/kernel/parallel_compiler.ex:100: anonymous fn/4 in Kernel.ParallelCompiler.spawn_compilers/8

$ 

我使用 web / models / user.ex 的确切README副本：

defmodule MyApp.User do
  use MyApp.Web, :model
  use Arc.Ecto.Schema

  schema "users" do
    field :name,   :string
    field :avatar, MyApp.Avatar.Type
  end

  @required_fields ~w()
  @optional_fields ~w(name)

  @required_file_fields ~w()
  @optional_file_fields ~w(avatar)

  @doc """
  Creates a changeset based on the `data` and `params`.

  If no params are provided, an invalid changeset is returned
  with no validation performed.
  """
  def changeset(user, params \\ :invalid) do
    user
    |> cast(params, @required_fields, @optional_fields)
    |> cast_attachments(params, @required_file_fields, @optional_file_fields)
  end
end

网络/上传/ avatar.ex

defmodule MyApp.Avatar do
  use Arc.Definition
  use Arc.Ecto.Definition

  @versions [:original]
end

mix.exs

defmodule MyApp.Mixfile do
  use Mix.Project

  [...]

  # Specifies your project dependencies.
  #
  # Type `mix help deps` for examples and options.
  defp deps do
    [{:phoenix, "~> 1.1.0"},
     {:phoenix_ecto, "~> 2.0"},
     {:mariaex, ">= 0.0.0"},
     {:phoenix_html, "~> 2.3"},
     {:phoenix_live_reload, "~> 1.0", only: :dev},
     {:gettext, "~> 0.9"},
     {:cowboy, "~> 1.0"},
     {:arc, "~> 0.5.2"},
     {:arc_ecto, "~> 0.3.2"}]
  end

  # Aliases are shortcut or tasks specific to the current project.
  # For example, to create, migrate and run the seeds file at once:
  #
  #     $ mix ecto.setup
  #
  # See the documentation for `Mix` for more info on aliases.
  defp aliases do
    ["ecto.setup": ["ecto.create", "ecto.migrate", "run priv/repo/seeds.exs"],
     "ecto.reset": ["ecto.drop", "ecto.setup"]]
  end
end

用户控制器 web / controllers / user_controller.ex 未更改：

defmodule MyApp.UserController do
  use MyApp.Web, :controller

  alias MyApp.User

  plug :scrub_params, "user" when action in [:create, :update]

  def index(conn, _params) do
    users = Repo.all(User)
    render(conn, "index.html", users: users)
  end

  def new(conn, _params) do
    changeset = User.changeset(%User{})
    render(conn, "new.html", changeset: changeset)
  end

  def create(conn, %{"user" => user_params}) do
    changeset = User.changeset(%User{}, user_params)

    case Repo.insert(changeset) do
      {:ok, _user} ->
        conn
        |> put_flash(:info, "User created successfully.")
        |> redirect(to: user_path(conn, :index))
      {:error, changeset} ->
        render(conn, "new.html", changeset: changeset)
    end
  end

  def show(conn, %{"id" => id}) do
    user = Repo.get!(User, id)
    render(conn, "show.html", user: user)
  end

  def edit(conn, %{"id" => id}) do
    user = Repo.get!(User, id)
    changeset = User.changeset(user)
    render(conn, "edit.html", user: user, changeset: changeset)
  end

  def update(conn, %{"id" => id, "user" => user_params}) do
    user = Repo.get!(User, id)
    changeset = User.changeset(user, user_params)

    case Repo.update(changeset) do
      {:ok, user} ->
        conn
        |> put_flash(:info, "User updated successfully.")
        |> redirect(to: user_path(conn, :show, user))
      {:error, changeset} ->
        render(conn, "edit.html", user: user, changeset: changeset)
    end
  end

  def delete(conn, %{"id" => id}) do
    user = Repo.get!(User, id)

    # Here we use delete! (with a bang) because we expect
    # it to always work (and if it does not, it will raise).
    Repo.delete!(user)

    conn
    |> put_flash(:info, "User deleted successfully.")
    |> redirect(to: user_path(conn, :index))
  end
end

Answer 1

此修复是在 web / models / user.ex 中使用use Acr.Ecto.Model代替Arc.Ecto.Schema：

defmodule MyApp.User do
  use MyApp.Web, :model
  use Arc.Ecto.Model

  [...]
end