想象一下,我们有一辆汽车和一个发动机型号,显然是一辆汽车has_one发动机.所以有汽车模型的代码

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

  schema "cars" do
    field :name,:string            

    has_one :engine,MyApp.Engine

    timestamps
  end

  def changeset(model,params \\ :empty) do
    model
    |> cast(params,~w(name),~w())
    |> validate_length(:name,min: 5,message: "No way it's that short")    
  end

end

和发动机型号

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

  schema "engines" do
    field :type,:string            

    belongs_to :car,MyApp.Car

    timestamps
  end

  def changeset(model,~w(type),~w())
    |> validate_length(:type,max: 10,message: "No way it's that long")    
  end

end

表单的简单模板 – >

<%= form_for @changeset,cars_path(@conn,:create),fn c -> %>

  <%= text_input c,:name %>

  <%= inputs_for c,:engine,fn e -> %>

    <%= text_input e,:type %>

  <% end %>  

  <button name="button" type="submit">Create</button>

<% end %>

和控制器 – >

defmodule MyApp.CarController do
  use MyApp.Web,:controller
  alias MyApp.Car
  alias MyApp.Engine

  plug :scrub_params,"car" when action in [:create]

  def new(conn,_params) do    
    changeset = Car.changeset(%Car{engine: %Engine{}})    
    render conn,"new.html",changeset: changeset
  end

  def create(conn,%{"car" => car_params}) do    
    engine_changeset = Engine.changeset(%Engine{},car_params["engine"])
    car_changeset = Car.changeset(%Car{engine: engine_changeset},car_params)
    if car_changeset.valid? do
      Repo.transaction fn ->
        car = Repo.insert!(car_changeset)
        engine = Ecto.Model.build(car,:engine)
        Repo.insert!(engine)
      end
      redirect conn,to: main_page_path(conn,:index)
    else
      render conn,changeset: car_changeset
    end
  end    

end

和一个有趣的博客文章,可以澄清一些事情 – > here