Ecto:变更集删除对父模型的更新

defmodule Blog.Article do
  use Ecto.Schema

  schema "articles" do
    field :title, :string
    has_many :comments, Blog.Comment

    timestamps()
  end

  def changeset(article, attrs) do
    article
    |> cast(attrs, [:title])
    |> validate_required([:title])
    |> put_assoc(:comments, [])
  end

  def delete_with_comments(article) do
    article
    |> Ecto.Changeset.change()
    |> Ecto.Changeset.delete()
    |> Ecto.Changeset.put_assoc(:comments, [])
  end
end

defmodule Blog.Comment do
  use Ecto.Schema

  schema "comments" do
    field :content, :string
    belongs_to :article, Blog.Article

    timestamps()
  end

  def changeset(comment, attrs) do
    comment
    |> cast(attrs, [:content])
    |> validate_required([:content])
  end
end