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

classCreateEvents<ActiveRecord::Migration

def  changecreate_table:events  do |t|

    t.string:title

    t.text:expression

    t.timestamps null:false

end

end

end

Task

classCreateTasks<ActiveRecord::Migration

        def   changecreate_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

classEvent<ActiveRecord::Base

    has_many:tasks

    accepts_nested_attributes_for:tasks,:allow_destroy=>true,:reject_if=>:all_blank

end

classTask<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? %>

<divid="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 %>

<divclass="field">

<%= f.label :title %><br>

<%= f.text_field :title %>

</div>

<divclass="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#######################

<divclass="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。