使用单个 form_with 在 Rails 中创建和编辑嵌套资源

Question

背景

在我的应用程序内部，系列 由许多书籍 组成。系列的 Show 页面允许用户查看系列中的所有书籍并使用表单向系列中添加新书。

Show 页面上列出的每本书都有一个 link 到该书的 Edit 页面。编辑页面包含 用于最初添加图书的相同表单。编辑书籍时，表格应自动填写书籍现有信息。

问题

如何配置我的 form_with 标签，使其既可以创建新书又可以编辑现有书（自动填写编辑表单）？我尝试了以下配置，但它们要么破坏了编辑页面，要么破坏了显示页面：

1. <%= form_with(model: [ @series, @series.books.build ], local: true) do |form| %>
   • 打破图书编辑页面
   • 错误：没有错误，但表单不会自动填充数据
2. <%= form_with(model: @book, url: series_book_path, local: true) do |form| %>
   • 休息系列显示页面
   • 错误：No route matches {:action=>"show", :controller=>"books", :id=>"6"}, missing required keys: [series_id]
3. <%= form_with(model: [:series, @book], local: true) do |form| %>
   • 休息系列显示页面
   • 错误：Undefined method 'model_name' for nil:NilClass
4. <%= form_with(model: [@series, @series.books.find(@book.id)], local: true) do |form| %>
   • 休息系列显示页面
   • 错误：undefined method 'id' for nil:NilClass
5. <%= form_with(model: @book, url: [@series, @book], local: true) do |form| %>
   • 在系列展示页面上提交新书时中断
   • 错误：No route matches [POST] "/series/6"

我参考过的资源：

• https://api.rubyonrails.org/v5.2.2/classes/ActionView/Helpers/FormHelper.html#method-i-form_with
• https://guides.rubyonrails.org/form_helpers.html
• https://guides.rubyonrails.org/routing.html#resource-routing-the-rails-default
• https://github.com/rails/rails/blob/master/actionview/lib/action_view/helpers/form_helper.rb

现有代码

下面是相关代码的精简部分，以及 link 它们在我当前 GitHub 存储库中的位置。

config/routes.rb

resources :series do
  resources :books
end

app/models/book.rb

class Book < ApplicationRecord
  belongs_to :series
end

app/models/series.rb

class Series < ApplicationRecord
  has_many :books, dependent: :destroy
end

db/schema.rb

create_table "books", force: :cascade do |t|
  t.integer "series_number"
  t.integer "year_published"
  t.integer "series_id"
  t.datetime "created_at", null: false
  t.datetime "updated_at", null: false
  t.index ["series_id"], name: "index_books_on_series_id"
end

create_table "series", force: :cascade do |t|
  t.string "title"
  t.datetime "created_at", null: false
  t.datetime "updated_at", null: false
end

app/views/series/show.html.erb

<%= render @series.books %>
<%= render 'books/form' %>

app/views/books/_book.html.erb

<%= link_to 'Edit', edit_series_book_path(book.series, book) %>

app/views/books/edit.html.erb

<%= render 'form' %>

app/views/books/_form.html.erb

<%= form_with(model: @book, url: [@series, @book], local: true) do |form| %>
  <%= form.label :series_number %>
  <%= form.number_field :series_number %>

  <%= form.label :year_published %>
  <%= form.number_field :year_published %>
<% end %>

app/controllers/books_controller.rb

class BooksController < ApplicationController
  def index
    @books = Book.all
  end

  def show
    @book = Book.find(params[:id])
  end

  def new
    @book = Book.new
  end

  def edit
    @series = Series.find(params[:series_id])
    @book = @series.books.find(params[:id])
  end

  def create
    @series = Series.find(params[:series_id])
    @book = @series.books.create(book_params)
    redirect_to series_path(@series)
  end

  def destroy
    @series = Series.find(params[:series_id])
    @book = @series.books.find(params[:id])
    @book.destroy
    redirect_to series_path(@series)
  end

  private
    def book_params
      params.require(:book).permit(:year_published, :series_number)
    end
end

路线

          Prefix Verb   URI Pattern                                 Controller#Action
        articles GET    /articles(.:format)                         articles#index
                 POST   /articles(.:format)                         articles#create
     new_article GET    /articles/new(.:format)                     articles#new
    edit_article GET    /articles/:id/edit(.:format)                articles#edit
         article GET    /articles/:id(.:format)                     articles#show
                 PATCH  /articles/:id(.:format)                     articles#update
                 PUT    /articles/:id(.:format)                     articles#update
                 DELETE /articles/:id(.:format)                     articles#destroy
    series_books GET    /series/:series_id/books(.:format)          books#index
                 POST   /series/:series_id/books(.:format)          books#create
 new_series_book GET    /series/:series_id/books/new(.:format)      books#new
edit_series_book GET    /series/:series_id/books/:id/edit(.:format) books#edit
     series_book GET    /series/:series_id/books/:id(.:format)      books#show
                 PATCH  /series/:series_id/books/:id(.:format)      books#update
                 PUT    /series/:series_id/books/:id(.:format)      books#update
                 DELETE /series/:series_id/books/:id(.:format)      books#destroy
    series_index GET    /series(.:format)                           series#index
                 POST   /series(.:format)                           series#create
      new_series GET    /series/new(.:format)                       series#new
     edit_series GET    /series/:id/edit(.:format)                  series#edit
          series GET    /series/:id(.:format)                       series#show
                 PATCH  /series/:id(.:format)                       series#update
                 PUT    /series/:id(.:format)                       series#update
                 DELETE /series/:id(.:format)                       series#destroy

Answer 1

您可以将数组传递给表单以处理嵌套和 "shallow" 路由：

<%= form_with(model: [@series, @book], local: true) do |form| %>

<% end %>

Rails 压缩数组（删除 nil 值），因此如果 @series 为 nil，则表单将退回到 book_url(@book) 或 books_url。但是，您需要从控制器正确处理设置 @series 和 @book。

class SeriesController < ApplicationController
  def show
    @series = Series.find(params[:id])
    @book = @series.books.new # used by the form
  end
end

您可以使用 local 变量在您的视图中处理此问题：

# app/views/books/_form.html.erb
<%= form_with(model: model, local: true) do |form| %>

<% end %>

# app/views/books/edit.html.erb
<%= render 'form', locals: { model: [@series, @book] } %>

# app/views/series/show.html.erb
<%= render 'books/form', locals: { model: [@series, @series.book.new] } %>

您还可以在路由中使用 shallow: true 选项来避免嵌套成员路由（显示、编辑、更新、销毁）：

resources :series do
  resources :books, shallow: true
end

这会让你做到：

# app/views/books/edit.html.erb
<%= render 'form', model: @book %>

# app/views/books/_book.html.erb
<%= link_to 'Edit', edit_book_path(book) %>