Elixir 外部关系，不插入外键ID

副食品， 我正在学习EXTO，我正在尝试将关联的记录插入到另一个表中。这有点正常，因为正在插入记录，但外键字段为空

代码：

变更集的检查

%Ecto.Changeset{action: nil, changes: %{name: "Kategory 1"}, constraints: [],
 errors: [], filters: %{},
 model: %{__meta__: #Ecto.Schema.Metadata<:built>, __struct__: Hangman.Category,

   id: nil, inserted_at: nil, master_cat_id: 1,
   mastercat: #Ecto.Association.NotLoaded<association :mastercat is not loaded>,

   mastercat_id: nil, name: nil, updated_at: nil,
   words: #Ecto.Association.NotLoaded<association :words is not loaded>},
 optional: [], opts: [], params: %{"name" => "Kategory 1"}, repo: nil,
 required: [:name],
 types: %{id: :id, inserted_at: Ecto.DateTime, mastercat_id: :id, name: :string,

   updated_at: Ecto.DateTime,
   words: {:assoc,
    %Ecto.Association.Has{cardinality: :many, defaults: [], field: :words,
     on_cast: :changeset, on_delete: :nothing, on_replace: :raise,
     owner: Hangman.Category, owner_key: :id, queryable: Hangman.Word,
     related: Hangman.Word, related_key: :category_id}}}, valid?: true,
 validations: []}

%exto.Changeset{action:nil，changes:%{name:“Kategory 1”}，约束：[]，
错误：[]，筛选器：%{}，
模型：%{uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu，
id:nil，插入地址：nil，主目录id:1，
mastercat:#异位关联.未加载
外键是通过（故意未记录的）
异位关联
模块中的
Association\u key/2
函数从模块名称推断出来的：

iex(1)> Ecto.Association.association_key(User, :id)
:user_id
iex(3)> Ecto.Association.association_key(FooBar, :id)           
:foo_bar_id
iex(5)> Ecto.Association.association_key(MasterCat, :id)
:master_cat_id

将架构更改为使用显式外键字段名：

   schema "categories" do
    field :name, :string

    has_many :words, Hangman.Word
    belongs_to :mastercat, Hangman.MasterCat, foreign_key: :master_cat_id

    timestamps
  end

经过一点修补，它成功了！非常感谢。另外，请不要使用“changeset.valid？”，使用
case Repo.insert（…）对结果进行
和模式匹配。@JoséValim非常感谢您提供的提示
   schema "categories" do
    field :name, :string

    has_many :words, Hangman.Word
    belongs_to :mastercat, Hangman.MasterCat, foreign_key: :master_cat_id

    timestamps
  end