我想从多个表中获取数据

Question

我想从tag/show.html.erb中获取如下所示的多对多关系表（Tag-Service-Category）中的数据。

class Tag < ActiveRecord::Base 
    has_many :service_tags 
    has_many :services, through: :service_tags 
end 

class ServiceTag < ActiveRecord::Base 
    belongs_to :service 
    belongs_to :tag 
end 
class Service < ActiveRecord::Base 
    has_many :service_tags 
    has_many :tags, through: :service_tags 
    has_many :service_categories 
    has_many :categories, through: :service_categories 
end 
class ServiceCategory < ActiveRecord::Base 
    belongs_to :service 
    belongs_to :category 
end 
class Category < ActiveRecord::Base 
    has_many :service_categories 
    has_many :services, through: :service_categories 
end 

我写了这样的代码，但它不工作。 @tag = Tag.find（PARAMS [：编号]）

<% @tag.services.each do |service| %> 
<% service.categories.each do |category| %> 
     <span class="category" class="<%= category.id %>"><%= category.name %></span> 
     <% end %> 
<% end %> 

控制器/ tags_controller.rb

class TagsController < ApplicationController 
    def show 
     @tag = Tag.find(params[:id]) 
     @tags = Tag.all 
    end 
end 

Answer 1

虽然你有分贝的关系是正确的，你仍然需要叫出连接模型。因为你正在做一对双关系，所以你需要创建一个中间数组。尝试将此添加到您的视图中：

<% services_array = [] %> 
<% @tag.service_tags each do |service_tag| %> 
    <% services_array << service_tag.service %> 
<% end %> 
<% services_array.each do |service| %> 
    <span class="category"> 
    <%= service.service_category.category.id %> 
    <%= service.service_category.category.name %> 
    </span> 
<% end %>