elixir - Ecto 去除预紧力

Question

有什么办法可以逆向预加载吗？

%Post{
  comments: []
}

posts = Repo.all(Post) |> Repo.unload(:comments)

%Post{
  comments: #Ecto.Association.NotLoaded<association :comments is not loaded>,
}

Answer 1

Ecto.Association.NotLoaded 是一个普通的简单结构，所以你可能相对容易地实现这个 unpreload你自己:

defmodule Unpreloader do
  def forget(struct, field, cardinality \\ :one) do
    %{struct | 
      field => %Ecto.Association.NotLoaded{
        __field__: field,
        __owner__: struct.__struct__,
        __cardinality__: cardinality
      }
    }
  end
end

稍后将其用作:

Unpreloader.forget(%Post{....}, :comments)