elixir - 如何自定义 Phoenix id

Question

使用 Phoenix 框架，:id, :integer会自动生成。
http://www.phoenixframework.org/docs/ecto-custom-primary-keys

但我不希望它自动生成并使用自定义 id 字段，例如 :id, :string ，很像这样
http://ruby-journal.com/how-to-override-default-primary-key-id-in-rails/

要设置

defmodule MyApp.Item do
  use MyApp.Web, :model

  # @primary_key {:id, :id, autogenerate: false}
  schema "items" do
    field :id, :string, autogenerate: false # some unique id string
    field :type, :integer

它引发 ** (ArgumentError) field/association :id is already set on schema https://github.com/elixir-lang/ecto/blob/db1f9ccdcc01f5abffcab0b5e0732eeecd93aa19/lib/ecto/schema.ex#L1327

Answer 1

我面临两个问题。

两者 @primary_key {:id, :id, autogenerate: false}和 fields :id子句不能在架构定义中。

这是解决方案

defmodule MyApp.Item do
  use MyApp.Web, :model

  @primary_key {:id, :string, []}
  schema "items" do
    # field :id, :string <- no need!

为了避免自动生成的 id，我只需要编辑迁移文件

像这样

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

  def change do
    create table(:items, primary_key: false) do
      add :id, :string, primary_key: true

最后，我可以执行 mix ecto.migrate并且可以得到下面的表定义

mysql> SHOW CREATE TABLE items;
| items | CREATE TABLE `builds` (
  `id` varchar(255) NOT NULL,

官方文件肯定是这样说的
http://www.phoenixframework.org/docs/ecto-custom-primary-keys

Let's take a look at the migration first, priv/repo/migrations/20150908003815_create_player.exs. We'll need to do two things. The first is to pass in a second argument - primary_key: false to the table/2 function so that it won't create a primary_key. Then we'll need to pass primary_key: true to the add/3 function for the name field to signal that it will be the primary_key instead.

但是一开始，你不想要列 id ，你只要做 create table(:items, primary_key: false)在迁移中，并编辑架构

defmodule MyApp.Item do
  use MyApp.Web, :model

  # @primary_key {:id, :string, []}
  @primary_key false # to avoid unnecessary IO scanning
  schema "items" do
    # field :id, :string <- no need!

虽然自行解决，但还是谢谢