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stackoverflow 上有很多关于 rails 复杂表单的问题，它们似乎都指向 Ryan Bates 关于这个主题的不错的 railscast 演示：part1和part2。

这对它的作用很好，但我没有看到解决您可能想要创建新的子对象或者您可能想要关联已经存在的对象的情况的问题。

就我而言，我希望用户能够创建一个新事件。作为其中的一部分，他们需要说明谁参与了该事件。大约一半的时间，被添加到事件中的人员已经存在于数据库中。在这种情况下，应该鼓励用户使用那些现有记录而不是创建新记录。

有关如何处理表单中这种复杂性的任何建议？

作为解决方案的一部分，您是否建议，如果用户在提交父对象之前找不到应用程序继续运行并动态创建它的人？我的想法（但有兴趣听取建议）是用户应该使用现有的 Person 记录（如果有的话），但是如果用户需要创建一个 NEW Person 记录，那么这个新记录不会提交到数据库，直到用户提交事件。想法？

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嗨，要完成您需要做的事情，有几个简单的步骤可以遵循： 1）在模型类（在您的情况下为 Incident 和 Person 类）中，确保放置如下内容：

class Incident < ActiveRecord::Base
    has_and_belongs_to_many :people
    # Note if you want to be able to remove a person from the Incident form (to de-associate) put true in :allow_destroy => true on the accepts_nested_attributes_for
    accepts_nested_attributes_for :people, :allow_destroy => false, :reject_if => :all_blank
    validates_associated :people #so you won't be able to save invalid people objects
    attr_accessible :date_occur, :location, :people_attributes # note the :people_attributes here
    #do your Incident validations as usual...        
end

class Person < ActiveRecord::Base
    has_and_belongs_to_many :incidents
    #the following line it's to allow mass assignment, basically it will allow you to create people from the Incident form
    attr_accessible :first_name, :last_name, :dob 
    #do your Person validations as usual...
end

2) 在视图方面，最简单的方法是修改事件表单文件 (app/view/incidents/_form.html.erb) 以允许用户将现有人员和创建新人员分配给事件：

# app/view/incidents/_form.html.erb

<%= semantic_form_for(@incident) do |f| %>
    <% if @incident.errors.any? %>
    <div id="error_explanation">
        <h2><%= pluralize(@incident.errors.count, "error") %> prohibited this incident from being saved:</h2>
        <ul>
            <% @incident.errors.full_messages.each do |msg| %>
                <li><%= msg %></li>
            <% end %>
        </ul>
    </div>
    <% end %>

    <div class="field">
        <%= f.label :date_occur %><br />
        <%= f.datetime_select :date_occur %>
    </div>
    <div class="field">
        <%= f.label :location %><br />
        <%= f.text_field :location %>
    </div>

    <%= f.input :people, :as => :select, :collection=>Hash[Person.all.map { |p| [p.first_name + ' - ' + p.last_name, p.id] }] %>

    <%= f.fields_for :people, Person.new() do |new_person_form| %>
        <div class="incident-people new-person">
            <%= new_person_form.inputs    :name=>'Add New person' do %>
                <%= new_person_form.input :first_name, :label=>'First Name: ' %>
                <%= new_person_form.input :last_name, :label=>'Last Name: ' %>
                <%= new_person_form.input :dob, :label=>'Date of birth: ' %>
            <% end %>
        </div>
    <% end %>


  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

3）最后，您需要修改您的更新并为事件控制器创建方法，如下所示：

# app/controllers/incident_controller.rb
def create
    selected_people = params[:incident][:person_ids].keep_if{ |v| v.present? }
    params[:incident].delete(:person_ids)
    @incident = Incident.new(params[:incident])
    @incident.people = Person.find( selected_people )

    respond_to do |format|
        if @incident.save
            format.html { redirect_to @incident, notice: 'Incident was successfully created.' }
            format.json { render json: @incident, status: :created, location: @incident }
        else
            format.html { render action: "new" }
            format.json { render json: @incident.errors, status: :unprocessable_entity }
        end
    end
end

def update
    selected_people = params[:incident][:person_ids].keep_if{ |v| v.present? }
    params[:incident].delete(:person_ids)
    @incident = Incident.find(params[:id])
    @incident.people = Person.find( selected_people )
    respond_to do |format|
        if @incident.update_attributes(params[:incident])
            format.html { redirect_to @incident, notice: 'Incident was successfully updated.' }
            format.json { head :no_content }
        else
            format.html { render action: "edit" }
            format.json { render json: @incident.errors, status: :unprocessable_entity }
        end
    end
end

就是这样，如果您需要进一步的帮助，请告诉我。联邦快递

于 2012-07-10T23:11:41.417 回答