我的问题是我遇到了accepts_nested_attributes_for的限制，因此我需要弄清楚如何自行复制该功能以获得更大的灵活性。 （请参阅下文，了解究竟是什么让我感到高兴。）所以我的问题是：如果我想模仿并增加accepts_nested_attributes_for，我的表单，控制器和模型应该是什么样的？真正的诀窍是我需要能够用现有的关联/属性更新现有的和新的模型。
我正在构建一个使用嵌套表单的应用。我最初使用此RailsCast作为蓝图（利用accepts_nested_attributes_for）：Railscast 196: Nested Model Form。
我的应用程序是带有作业（任务）的清单，我让用户更新清单（名称，描述）并在单个表单中添加/删除关联的作业。这很好用，但是当我将这个问题合并到我的应用程序的另一个方面时，我遇到了问题：历史记录通过版本控制。
我的应用程序的一个重要部分是我需要记录模型和关联的历史信息。我最终推出了自己的版本控制（here是我在描述我的决策过程/考虑因素的问题），其中很大一部分是我需要创建旧版本的新版本的工作流程，进行更新到新版本，归档旧版本。这对于用户来说是不可见的，用户将体验看作只是通过UI更新模型。
代码 - 模型
#checklist.rb
class Checklist < ActiveRecord::Base
has_many :jobs, :through => :checklists_jobs
accepts_nested_attributes_for :jobs, :reject_if => lambda { |a| a[:name].blank? }, :allow_destroy => true
end
#job.rb
class Job < ActiveRecord::Base
has_many :checklists, :through => :checklists_jobs
end
代码 - 当前表单（注意：@jobs在检查清单控制器编辑操作中被定义为此清单的未归档作业; @checklist也是如此）
<%= simple_form_for @checklist, :html => { :class => 'form-inline' } do |f| %>
<fieldset>
<legend><%= controller.action_name.capitalize %> Checklist</legend><br>
<%= f.input :name, :input_html => { :rows => 1 }, :placeholder => 'Name the Checklist...', :class => 'autoresizer' %>
<%= f.input :description, :input_html => { :rows => 3 }, :placeholder => 'Optional description...', :class => 'autoresizer' %>
<legend>Jobs on this Checklist - [Name] [Description]</legend>
<%= f.fields_for :jobs, @jobs, :html => { :class => 'form-inline' } do |j| %>
<%= render "job_fields_disabled", :j => j %>
<% end %>
</br>
<p><%= link_to_add_fields "+", f, :jobs %></p>
<div class="form-actions">
<%= f.submit nil, :class => 'btn btn-primary' %>
<%= link_to 'Cancel', checklists_path, :class => 'btn' %>
</div>
</fieldset>
<% end %>
代码 - 来自checklists_controller.rb的代码段＃更新
def update
@oldChecklist = Checklist.find(params[:id])
# Do some checks to determine if we need to do the new copy/archive stuff
@newChecklist = @oldChecklist.dup
@newChecklist.parent_id = (@oldChecklist.parent_id == 0) ? @oldChecklist.id : @oldChecklist.parent_id
@newChecklist.predecessor_id = @oldChecklist.id
@newChecklist.version = (@oldChecklist.version + 1)
@newChecklist.save
# Now I've got a new checklist that looks like the old one (with some updated versioning info).
# For the jobs associated with the old checklist, do some similar archiving and creating new versions IN THE JOIN TABLE
@oldChecklist.checklists_jobs.archived_state(:false).each do |u|
x = u.dup
x.checklist_id = @newChecklist.id
x.save
u.archive
u.save
end
# Now the new checklist's join table entries look like the old checklist's entries did
# BEFORE the form was submitted; but I want to update the NEW Checklist so it reflects
# the updates made in the form that was submitted.
# Part of the params[:checklist] has is "jobs_attributes", which is handled by
# accepts_nested_attributes_for. The problem is I can't really manipulate that hash very
# well, and I can't do a direct update with those attributes on my NEW model (as I'm
# trying in the next line) due to a built-in limitation.
@newChecklist.update_attributes(params[:checklist])
这就是我遇到accepts_nested_attributes_for限制的地方（它很好地记录了here。我得到了“找不到具有ID = X的模型2的Model1与ID = Y”的异常，这基本上是 - 设计的。
那么，我如何创建多个嵌套模型并在父模型的表单上添加/删除它们，类似于accepts_nested_attributes_for，但我自己呢？
我见过的选项 - 这些是最好的选择之一吗？ 真正的诀窍是我需要能够使用现有的关联/属性更新现有的和新的模型。我无法链接它们，所以我只是命名它们。
Redtape（在github上） Virtus（也是github）
感谢您的帮助！
答案 0 :(得分：5)
您可能想要删除复杂的accepts_nested内容并创建自定义类或模块以包含所需的所有步骤。
这篇文章中有一些有用的东西
http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/
特别是第3点
答案 1 :(得分：1)
由于马里奥对我的问题发表评论并询问我是否解决了这个问题，我想我会分享我的解决方案。
我应该说，我确信这不是一个非常优雅的解决方案，而且它不是很棒的代码。但这是我提出的，它的确有效。由于这个问题非常技术性，我不会在这里发布伪代码 - 我发布了Checklist模型和Checklists控制器更新操作的完整代码（无论如何，这些代码部分适用于此问题）。我也非常确定我的事务块实际上没有做任何事情（我需要解决这些问题）。
基本思路是我手动打破了更新操作。我不是依赖update_attributes（和accepts_nested_attributes_for），而是分两个阶段手动更新清单：
我认为这里有一些“提交”的东西是可以安全忽略的（基本上是逻辑来判断核对清单是如何变化的 - 如果没有任何提交（核对表的历史数据的记录）那么只是更新没有进行任何归档或添加/减去工作的东西的核对清单。
我不知道这是否会有所帮助，但无论如何它都在这里。
代码 - checklist.rb（型号）
class Checklist < ActiveRecord::Base
scope :archived_state, lambda {|s| where(:archived => s) }
belongs_to :creator, :class_name => "User", :foreign_key => "creator_id"
has_many :submissions
has_many :checklists_jobs, :dependent => :destroy, :order => 'checklists_jobs.job_position'#, :conditions => {'archived_at' => nil}
has_many :jobs, :through => :checklists_jobs
has_many :unarchived_jobs, :through => :checklists_jobs,
:source => :job,
:conditions => ['checklists_jobs.archived = ?', false], :order => 'checklists_jobs.job_position'
has_many :checklists_workdays, :dependent => :destroy
has_many :workdays, :through => :checklists_workdays
def make_child_of(old_checklist)
self.parent_id = (old_checklist.parent_id == 0) ? old_checklist.id : old_checklist.parent_id
self.predecessor_id = old_checklist.id
self.version = (old_checklist.version + 1)
end
def set_new_jobs(new_jobs)
new_jobs.to_a.each do |job|
self.unarchived_jobs << Job.find(job) unless job.nil?
end
end
def set_jobs_attributes(jobs_attributes, old_checklist)
jobs_attributes.each do |key, entry|
# Job already exists and should have a CJ
if entry[:id] && !(entry[:_destroy] == '1')
old_cj = old_checklist.checklists_jobs.archived_state(:false).find_by_job_id(entry[:id])
new_cj = ChecklistsJob.new job_position: old_cj.job_position, job_required: old_cj.job_required
new_cj.checklist = self
new_cj.job = old_cj.job
new_cj.save!
# New job, should be created and added to new checklist only
else
unless entry[:_destroy] == '1'
entry.delete :_destroy
self.jobs << Job.new(entry)
end
end
end
end
def set_checklists_workdays!(old_checklist)
old_checklist.checklists_workdays.archived_state(:false).each do |old_cw|
new_cw = ChecklistsWorkday.new checklist_position: old_cw.checklist_position
new_cw.checklist = self
new_cw.workday = old_cw.workday
new_cw.save!
old_cw.archive
old_cw.save!
end
end
def update_checklists_jobs!(jobs_attributes)
jobs_attributes.each do |key, entry|
if entry[:id] # Job was on self when #edit was called
old_cj = self.checklists_jobs.archived_state(:false).find_by_job_id(entry[:id])
#puts "OLD!! "+old_cj.id.to_s
unless entry[:_destroy] == '1'
new_cj = ChecklistsJob.new job_position: old_cj.job_position, job_required: old_cj.job_required
new_cj.checklist = self
new_cj.job = old_cj.job
new_cj.save!
end
old_cj.archive
old_cj.save!
else # Job was created on this checklist
unless entry[:_destroy] == '1'
entry.delete :_destroy
self.jobs << Job.new(entry)
end
end
end
end
end
代码 - checklists_controller.rb（控制器）
class ChecklistsController < ApplicationController
before_filter :admin_user
def update
@checklist = Checklist.find(params[:id])
@testChecklist = Checklist.find(params[:id])
@oldChecklist = Checklist.find(params[:id])
@job_list = @checklist.unarchived_jobs.exists? ? Job.archived_state(:false).where( 'id not in (?)', @checklist.unarchived_jobs) : Job.archived_state(:false)
checklist_ok = false
# If the job is on a submission, do archiving/copying; else just update it
if @checklist.submissions.count > 0
puts "HERE A"
# This block will tell me if I need to make new copies or not
@testChecklist.attributes=(params[:checklist])
jobs_attributes = params[:checklist][:jobs_attributes]
if @testChecklist.changed?
puts "HERE 1"
params[:checklist].delete :jobs_attributes
@newChecklist = Checklist.new(params[:checklist])
@newChecklist.creator = current_user
@newChecklist.make_child_of(@oldChecklist)
@newChecklist.set_new_jobs(params[:new_jobs])
begin
ActiveRecord::Base.transaction do
@newChecklist.set_jobs_attributes(jobs_attributes, @oldChecklist) if jobs_attributes
@newChecklist.set_checklists_workdays!(@oldChecklist)
@newChecklist.save!
@oldChecklist.archive
@oldChecklist.save!
@checklist = @newChecklist
checklist_ok = true
end
rescue ActiveRecord::RecordInvalid
# This is a NEW checklist, so it's acting like it's "new" - WRONG?
puts "RESCUE 1"
@checklist = @newChecklist
@jobs = @newChecklist.jobs
checklist_ok = false
end
elsif @testChecklist.changed_for_autosave? || params.has_key?(:new_jobs)
puts "HERE 2"
# Associated Jobs have changed, so archive old checklists_jobs,
# then set checklists_jobs based on params[:checklist][:jobs_attributes] and [:new_jobs]
@checklist.set_new_jobs(params[:new_jobs])
begin
ActiveRecord::Base.transaction do
@checklist.update_checklists_jobs!(jobs_attributes) if jobs_attributes
@checklist.save!
checklist_ok = true
end
rescue ActiveRecord::RecordInvalid
puts "RESCUE 2"
@jobs = @checklist.unarchived_jobs
checklist_ok = false
end
else
checklist_ok = true # There were no changes to the Checklist or Jobs
end
else
puts "HERE B"
@checklist.set_new_jobs(params[:new_jobs])
begin
ActiveRecord::Base.transaction do
@checklist.update_attributes(params[:checklist])
checklist_ok = true
end
rescue ActiveRecord::RecordInvalid
puts "RESCUE B"
@jobs = @checklist.jobs
checklist_ok = false
end
end
respond_to do |format|
if checklist_ok
format.html { redirect_to @checklist, notice: 'List successfully updated.' }
format.json { head :no_content }
else
flash.now[:error] = 'There was a problem updating the List.'
format.html { render action: "edit" }
format.json { render json: @checklist.errors, status: :unprocessable_entity }
end
end
end
end
代码 - 核对清单
<%= form_for @checklist, :html => { :class => 'form-inline' } do |f| %>
<div>
<%= f.text_area :name, :rows => 1, :placeholder => 'Name the list...', :class => 'autoresizer checklist-name' %></br>
<%= f.text_area :description, :rows => 1, :placeholder => 'Optional description...', :class => 'autoresizer' %>
</div>
<%= f.fields_for :jobs, :html => { :class => 'form-inline' } do |j| %>
<%= render "job_fields", :j => j %>
<% end %>
<span class="add-new-job-link"><%= link_to_add_fields "add a new job", f, :jobs %></span>
<div class="form-actions">
<%= f.submit nil, :class => 'btn btn-primary' %>
<%= link_to 'Cancel', checklists_path, :class => 'btn' %>
</div>
<% unless @job_list.empty? %>
<legend>Add jobs from the Job Bank</legend>
<% @job_list.each do |job| %>
<div class="toggle">
<label class="checkbox text-justify" for="<%=dom_id(job)%>">
<%= check_box_tag "new_jobs[]", job.id, false, id: dom_id(job) %><strong><%= job.name %></strong> <small><%= job.description %></small>
</label>
</div>
<% end %>
<div class="form-actions">
<%= f.submit nil, :class => 'btn btn-primary' %>
<%= link_to 'Cancel', checklists_path, :class => 'btn' %>
</div>
<% end %>
<% end %>