加载其他模型集合以进行新的，编辑更新和创建操作的最合理方式是什么？ [英] What's the rails way to load other models collections for new, edit update and create actions?

问题描述

对于在新的ProductController中加载类别模型的最佳方式是什么，如何编辑更新并创建操作

How is the best way to load Category model, for ProductController in new, edit update and create actions

产品具有类别集合

class Product < ActiveRecord::Base
  has_many :categories
end 

始终用于新建，编辑，创建和更新操作，我需要加载类别集合以填充check_box_tag列表

Always for new, edit, create and update actions, I need to load the categories collection to populate a check_box_tag list

这种情况的婴儿步骤是：

The "baby steps" for this situation is:

class Admin::ProductsController < Admin::AdminApplicationController

 def new
   @product = Product.new
   @categories = Category.all
 end

 def edit
   @product = Product.find(params[:id])
   @categories = Category.all
 end

 def create
   @product = Product.new(params[:product])
   if @product.save
     flash[:notice] = 'Product was successfully created'
     redirect_to edit_admin_product_path(@product)
   else
     @categories = Category.all
     render :new
  end
 end

 def update
   @product = Product.find(params[:id])
   @product.update_attributes(params[:product])
   if @product.save
     flash[:notice] = 'Product was successfully updated'
     redirect_to edit_admin_product_path(@product)
   else
     @categories = Category.all
     render :edit
   end
 end
end 

我不想总是加载Category.all在diff中出于相同目的的错误情况

I don't want to load always Category.all in different situations for same purpose

选项：

首先-在视图上加载类别：

First - load categories over the view:

<% Category.all.each do |cat| %>
  <li>
    <%= check_box_tag .... %>
  </li>
<% end %>

：/

第二-负载类别在ProductsHelper上：

Second - load categories over the ProductsHelper :

module ProductsHelper

  def categories
   Category.all
  end

end

：/

第三-是否存在类似 before_render的过滤器？

"Third" - Exist a filter like 'before_render'?

class Admin::ProductsController < Admin::AdminApplicationController

  before_render :load_categories :edit, :new

  def load_categories
    @categories = Category.all
  end

end

：D：D：D

在这种情况下会怎样？

What's the rails way for this situations?

最好的问候，
Pablo Cantero

Best Regards, Pablo Cantero

推荐答案

在您的控制器，或者如果需要，在application_controller.rb中：

In your controller, or if needed elsewhere, in application_controller.rb:

def all_categories
  @all_categories ||= Category.all
end
helper_method :all_categories

第一次调用它将点击数据库，稍后它将返回控制器实例变量。

The first time it's called, it will hit the db, and later it will return the controller instance variable.

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