elixir - 为什么我得到＃Ecto.Association.NotLoaded？

Question

我有团队，每个团队都有用户，因此有一个联接表将用户链接到团队，这是多对多关系，这是我的模型：

defmodule App.Team do
  use App.Web, :model

  schema "teams" do
    field :owner_id, :integer
    has_many :team_users, {"team_user", App.TeamUser}
  end

end
defmodule App.User do
  use App.Web, :model

  schema "users" do
    # field :email, :string
    has_many :team_user, App.TeamUser
  end
end

这是联接模型：

defmodule App.TeamUser do
  use App.Web, :model

  @primary_key false
  schema "team_user" do
    belongs_to :user, App.User
    belongs_to :team, App.Team
  end

end

如果我运行查询以获取一个用户的所有团队以及所有结果团队的用户，如下所示：

teams_users =
      from(t in Team, where: t.owner_id == ^user_id)
      |> Repo.all()
      |> Repo.preload(:team_users)

我得到此日志：

[%App.Team{__meta__: #Ecto.Schema.Metadata<:loaded>, id: 1,
  is_base_team: true, owner_id: 3,
  team_users: [%App.TeamUser{__meta__: #Ecto.Schema.Metadata<:loaded>,
    team: #Ecto.Association.NotLoaded<association :team is not loaded>,
    team_id: 1,
    user: #Ecto.Association.NotLoaded<association :user is not loaded>,
    user_id: 3},
   %App.TeamUser{__meta__: #Ecto.Schema.Metadata<:loaded>,
    team: #Ecto.Association.NotLoaded<association :team is not loaded>,
    team_id: 1,
    user: #Ecto.Association.NotLoaded<association :user is not loaded>,
    user_id: 4},
   %App.TeamUser{__meta__: #Ecto.Schema.Metadata<:loaded>,
    team: #Ecto.Association.NotLoaded<association :team is not loaded>,
    team_id: 1,
    user: #Ecto.Association.NotLoaded<association :user is not loaded>,
    user_id: 5}]}]

在日志中，我得到了ID为1的团队，其ID为（3，4，5）的所有用户。
但是为什么我得到 user: #Ecto.Association.NotLoaded<association :user is not loaded>？我没有要求以任何方式在该ID上加载用户。.为什么我会收到这样的警告？

我正在使用 {:phoenix_ecto, "~> 3.0-rc}

Answer 1

您需要预加载:user和:team_users：

teams_users =
  from(t in Team, where: t.owner_id == ^user_id)
  |> Repo.all()
  |> Repo.preload(team_users: :user)

文档中有关于嵌套关联的部分。 https://hexdocs.pm/ecto/Ecto.Query.html#preload/3