如何在 Rails 4 中创建嵌套表单

Question

我试图让用户通过他们各自的连接表（锻炼设备，锻炼肌肉）在多对多关系中创建带有设备和肌肉的练习。我已经获得了用于在每次锻炼中添加一个设备/肌肉的表单，但无法弄清楚如何添加链接以动态添加另一个字段。

我查看了RailsCasts、this post，并在previous post of my own 上将其作为附带问题提出，但根本无法使用此功能。我对 Rails 4 还很陌生，并且仍在尝试学习 Javascript，但我希望能详细说明如何以 Rails 4 的方式设置它！

我的模特：

# id        :integer
# name      :string
# is_public :boolean
Exercise
    has_many :exercise_equipment
    has_many :equipment, :through => :exercise_equipment
    accepts_nested_attributes_for :exercise_equipment


# id           :integer
# exercise_id  :integer
# equipment_id :integer
# optional     :boolean
ExerciseEquipment
    belongs_to :exercise
    belongs_to :equipment
    accepts_nested_attributes_for :equipment


# id   :integer
# name :string
Equipment
    has_many :exercise_equipment
    has_many :exercises, :through => :exercise_equipment

我的控制器方法：

def new
  @exercise = Exercise.new
  @exercise.exercise_equipment.build
  @exercise.exercise_muscles.build
end

def create
  exercise = current_user.exercises.new( exercise_params )
  if exercise.save!
    redirect_to exercise
  else
    render 'new'
  end
end

views/exercises/new.html.erb

<h1>Create New Exercise</h1>

<%= form_for @exercise do |f| %>
  <%= render 'form', f: f %>
  <%= f.submit "New Exercise" %>
<% end %>

视图/练习/_form.html.erb

<%= f.label :name %><br />
<%= f.text_field :name, autofocus: true %>

<%= f.check_box :is_public %> Public

<%= f.fields_for :exercise_muscles do |emf| %>
  <%= emf.collection_select :muscle_id, Muscle.all, :id, :name, { include_hidden: false } %>
<% end %>

<%= f.fields_for :exercise_equipment do |eef| %>
  <%= eef.collection_select :equipment_id, Equipment.all, :id, :name, { include_hidden: false } %>
  <%= eef.check_box :optional %> Optional
<% end %>

Answer 1

Ajax

无法弄清楚如何添加链接以将另一个字段添加到表单 在飞行中

这样做的“Rails 方式”是从ajax 请求中“拉”出fields_for 块的新实例。

推荐 Ajax 的原因是因为它是“Rails 方式”——完全模块化和可扩展：

#config/routes.rb
resources :exercises do
   get :add_field, on: :collection
end

#app/models/exercise.rb
Class Exercise < ActiveRecord::Base
   ...
   def self.build #-> allows you to call a single method
      exercise = self.new
      exercise.exercise_equipment.build
      exercise.exercise_muscles.build
      return
   end
end

#app/controllers/exercises_controller.rb
Class ExercisesController < ApplicationController
   def add_field
      @exercise = Exercise.build
      respond_to do |format|
         format.html
         format.js
      end
   end
end

#app/views/exercises/new.html.erb
<%= form_for @exercise do |f| %>
   <%= render "fields", locals: { f: f } %>
   <%= f.submit %>
<% end %>

#app/views/exercises/add_field.js.erb
$("#form_element").append("<%=j render "exercises/form", locals: { exercise: @exercise } %>");

#app/views/exercises/_form.html.erb
<%= form_for exercise do |f| %>
   <%= render "fields", locals: { f: f } %>
<% end %>

#app/views/exercises/_fields.html.erb
<%= f.fields_for :exercise_muscles, child_index: Time.now.to_i do |emf| %>
    <%= emf.collection_select :muscle_id, Muscle.all, :id, :name, { include_hidden: false } %>
<% end %>
<%= link_to "New Field", exercises_add_fields_path, remote: :true %>

<%= f.fields_for :exercise_equipment, child_index: Time.now.to_i do |eef| %>
   <%= eef.collection_select :equipment_id, Equipment.all, :id, :name, { include_hidden: false } %>
   <%= eef.check_box :optional %> Optional
<% end %>
<%= link_to "New Field", exercises_add_fields_path, remote: :true %>

这将使您能够通过 ajax 调用创建字段；这是正确的做法

Answer 2

在尝试使用 Rich 的解决方案后，我想找到一个在所用代码方面更简洁的解决方案。我找到了 gem Cocoon，它非常好用，而且集成起来非常简单。

我的主要 _form 视图：

<div class="form-group">
  <%= f.label :name %><br />
  <%= f.text_field :name, autofocus: true %>
</div>

<div class="form-group">
  <%= f.check_box :is_public %> Public
</div>

<div class="form-group">
  <%= f.fields_for :exercise_muscles do |emf| %>
    <%= render 'exercise_muscle_fields', :f => emf %>
  <% end %>
  <%= link_to_add_association 'Add Muscle', f, :exercise_muscles %>
</div>

<div class="form-group">
  <%= f.fields_for :exercise_equipment do |eef| %>
    <%= render 'exercise_equipment_fields', :f => eef %>
  <% end %>
  <%= link_to_add_association 'Add Equipment', f, :exercise_equipment %>
</div>

从这里可以看出，添加一个简单的“link_to_add_association”方法会在后台处理所有的 Javascript。对于未来的读者，以下是每个表单组包含的部分：

_exercise_muscle_fields：

<%= f.collection_select :muscle_id, Muscle.all.order( 'muscle_group_id ASC' ), :id, :name, { include_hidden: false } %>

_exercise_equipment_fields：

<%= f.collection_select :equipment_id, Equipment.all.order( 'name ASC' ), :id, :name, { include_hidden: false } %>
<%= f.check_box :optional %> Optional