如何編輯預先存在的 model 以添加新創建的關聯 class？

Question

我在實時應用程序中有一套公寓 object。 我決定為每個公寓添加一個相關的便利設施 object 來描述公寓有哪些便利設施。 便利設施 model 顯示

class Amenity < ApplicationRecord
  belongs_to :apartment
end

公寓 model 展示

class Apartment < ApplicationRecord
has_one :amenity, dependent: :destroy
  accepts_nested_attributes_for :amenity
end

使用相關設施創建新公寓效果很好公寓 controller 顯示

  def new
   @apartment = Apartment.new
   @apartment.build_amenity
  end

一旦使用便利設施創建公寓，就可以輕松編輯便利設施公寓 controller 顯示

def edit; end

但是，對於現有公寓，編輯表單不會顯示要填寫的便利設施（很可能是因為沒有與現有公寓相關聯的預先創建的便利設施）。 我嘗試更改 controller 中的編輯操作如下

def edit
 @apartment = Apartment.find_or_initialize_by(params[:id])
end

def edit
 @apartment = Apartment.find_or_create_by(params[:id])
end

但是這兩個選項都不能顯示表單。 The form works well when creating brand new apartment with associated amenities so there is something in the controller missing (an equivalent of @apartment.build_amenity in the edit controller that would instantiate a new amenity object associated with pre-existing apartment that I want to edit ）。 你能幫我解決這個問題嗎？

這是表單代碼（非常基本）

<%= form.fields_for :amenity, @apartment.amenity do |p| %>
...
<% end %>

Answer 1

要編輯現有的apartment ，您可以使用includes預加載amenity

def edit
 @apartment = Apartment.includes(:amenity).find_or_initialize_by(id: params[:id])
end

通知

<%= form.fields_for :amenity, (@apartment.amenity || @apartment.build_amenity) do |p| %>

Answer 2

我通過將 false 作為默認值直接添加到表中來解決了這個問題

  create_table "amenities", force: :cascade do |t|
    t.boolean "towels", default: false
    t.boolean "bed_linen", default: false
    t.boolean "toilet_paper", default: false
    t.boolean "soap", default: false
    ...

默認情況下具有 false 值而不是 nil 可以使表單出現。