nested_form笔记

1. 安装gem包

gem 'nested_form'

增加jquery效果,在application.js中添加

//= require jquery_nested_form

执行bundle install

2. 新建两个Model

Event

class CreateEvents < ActiveRecord::Migration
  def change
    create_table :events do |t|
      t.string :title
      t.text :expression

      t.timestamps null: false
    end
  end
end

Task

class CreateTasks < ActiveRecord::Migration
  def change
    create_table :tasks do |t|
      t.integer :event_id
      t.text :name
      t.text :dothing

      t.timestamps null: false
    end
  end
end

3. 确定Model之间的关系

class Event < ActiveRecord::Base
  has_many :tasks
  accepts_nested_attributes_for :tasks, :allow_destroy => true, :reject_if => :all_blank
end

class Task < ActiveRecord::Base
  belongs_to :event
end

4. 修改controller

def event_params
      params.require(:event).permit(:title, :expression, :tasks_attributes=>[:id, :name, :dothing, :_destroy])
    end

5. 修改view

<%= nested_form_for(@event) do |f| %>
  <% if @event.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@event.errors.count, "error") %> prohibited this event from being saved:</h2>

      <ul>
      <% @event.errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </div>
  <div class="field">
    <%= f.label :expression %><br>
    <%= f.text_area :expression %>
  </div>
###############################新增#######################
  <%= f.fields_for :tasks do |t| %>
    <%= t.text_field :name, :class => 'my_class', :mthd=>'clickd' %>
    <%= t.text_field :dothing %>
    <%=  t.link_to_remove "移除此待办事项" %>
  <% end %>
  <%=  f.link_to_add "新增待办事项", :tasks %>
###############################新增#######################
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

6. 解释

因为我们在model里面有加上:reject_if => :all_blank，所以如果把需要填入资料的地方都留白，就不会储存，同等于把这个数据删除；这个方法可以间接用来删除不想要的数据。
如果刚刚的设置有错误，可能就会发生一次增加多个数据、或是明明删了数据却有储存等窘境。