Rails has_many 通过表单，在连接模型中带有复选框和额外字段

Question

我正在尝试解决一个非常常见的（正如我所想的）任务。

共有三种模型：

class Product < ActiveRecord::Base  
  validates :name, presence: true

  has_many :categorizations
  has_many :categories, :through => :categorizations

  accepts_nested_attributes_for :categorizations
end

class Categorization < ActiveRecord::Base
  belongs_to :product
  belongs_to :category

  validates :description, presence: true # note the additional field here
end

class Category < ActiveRecord::Base
  validates :name, presence: true
end

当涉及到产品新建/编辑表单时，我的问题就开始了。

创建产品时，我需要检查它所属的类别（通过复选框）。我知道可以通过创建名称如“product[category_ids][]”的复选框来完成。但我还需要输入每个已检查关系的描述，该描述将存储在连接模型（分类）中。

我在复杂的表单、habtm 复选框等上看到了那些漂亮的 Railscast。我几乎一直在 StackOverflow 上搜索。但我还没有成功。

我发现一篇帖子描述了与我几乎完全相同的问题。最后一个答案对我来说有一定意义（看起来这是正确的方法）。但它实际上并不能很好地工作（即如果验证失败）。我希望类别始终以相同的顺序显示（以新/编辑表单；验证之前/之后），并且复选框在验证失败时保持在原来的位置，等等。

任何想法都值得赞赏。 我是 Rails 新手（从 CakePHP 切换过来），所以请耐心等待并尽可能详细地写。请指出我正确的方法！

谢谢。 :)

Answer 1

看来我想通了！这是我得到的：

我的模型：

class Product < ActiveRecord::Base
  has_many :categorizations, dependent: :destroy
  has_many :categories, through: :categorizations

  accepts_nested_attributes_for :categorizations, allow_destroy: true

  validates :name, presence: true

  def initialized_categorizations # this is the key method
    [].tap do |o|
      Category.all.each do |category|
        if c = categorizations.find { |c| c.category_id == category.id }
          o << c.tap { |c| c.enable ||= true }
        else
          o << Categorization.new(category: category)
        end
      end
    end
  end

end

class Category < ActiveRecord::Base
  has_many :categorizations, dependent: :destroy
  has_many :products, through: :categorizations

  validates :name, presence: true
end

class Categorization < ActiveRecord::Base
  belongs_to :product
  belongs_to :category

  validates :description, presence: true

  attr_accessor :enable # nice little thingy here
end

形式：

<%= form_for(@product) do |f| %>
  ...
  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>
  </div>

  <%= f.fields_for :categorizations, @product.initialized_categorizations do |builder| %>
    <% category = builder.object.category %>
    <%= builder.hidden_field :category_id %>

    <div class="field">
      <%= builder.label :enable, category.name %>
      <%= builder.check_box :enable %>
    </div>

    <div class="field">
      <%= builder.label :description %><br />
      <%= builder.text_field :description %>
    </div>
  <% end %>

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

和控制器：

class ProductsController < ApplicationController
  # use `before_action` instead of `before_filter` if you are using rails 5+ and above, because `before_filter` has been deprecated/removed in those versions of rails.
  before_filter :process_categorizations_attrs, only: [:create, :update]

  def process_categorizations_attrs
    params[:product][:categorizations_attributes].values.each do |cat_attr|
      cat_attr[:_destroy] = true if cat_attr[:enable] != '1'
    end
  end

  ...

  # all the rest is a standard scaffolded code

end

乍一看它工作得很好。我希望它不会以某种方式损坏..:)

谢谢大家。特别感谢 Sandip Ransing 参与讨论。我希望它对像我这样的人有用。

Answer 2

使用accepts_nested_attributes_for插入中间表即分类
视图表单看起来像 -

# make sure to build product categorizations at controller level if not already
class ProductsController < ApplicationController
  before_filter :build_product, :only => [:new]
  before_filter :load_product, :only => [:edit]
  before_filter :build_or_load_categorization, :only => [:new, :edit]

  def create
    @product.attributes = params[:product]
    if @product.save
      flash[:success] = I18n.t('product.create.success')
      redirect_to :action => :index
    else
      render_with_categorization(:new)
    end
  end 

  def update
    @product.attributes = params[:product]
    if @product.save
      flash[:success] = I18n.t('product.update.success')
      redirect_to :action => :index
    else
      render_with_categorization(:edit)
    end
  end

  private
  def build_product
    @product = Product.new
  end

  def load_product
    @product = Product.find_by_id(params[:id])
    @product || invalid_url
  end

  def build_or_load_categorization
    Category.where('id not in (?)', @product.categories).each do |c|
      @product.categorizations.new(:category => c)
    end
  end

  def render_with_categorization(template)
    build_or_load_categorization
    render :action => template
  end
end

内部视图

= form_for @product do |f|
  = f.fields_for :categorizations do |c|
   %label= c.object.category.name
   = c.check_box :category_id, {}, c.object.category_id, nil
   %label Description
   = c.text_field :description

Answer 3

我刚刚做了以下事情。它对我有用..

<%= f.label :category, "Category" %>
<%= f.select :category_ids, Category.order('name ASC').all.collect {|c| [c.name, c.id]}, {} %>