Question

我目前正在开发一种可安装的引擎。在发动机内我有以下两种型号：

  module Ems
    class Channel < ActiveRecord::Base
      has_and_belongs_to_many :categories
    end
  end

  module Ems
    class Category < ActiveRecord::Base
      has_and_belongs_to_many :channels
    end
  end

这些是db迁移文件：

  class CreateEmsChannels < ActiveRecord::Migration
    def change
      create_table :ems_channels do |t|
        t.string :slug
        t.string :name

        t.timestamps
      end
    end
  end

  class CreateEmsCategories < ActiveRecord::Migration
    def change
      create_table :ems_categories do |t|
        t.string :slug
        t.string :name
        t.text :strapline

        t.timestamps
      end
    end
  end


  class CreateEmsCategoriesChannels < ActiveRecord::Migration
    def up
      # Create the association table
      create_table :ems_categories_channels, :id => false do |t|
        t.integer :category_id, :null => false
        t.integer :channel_id, :null => false
      end

      # Add table index
      add_index :ems_categories_channels, [:category_id, :channel_id], :unique => true
    end
  end

当我尝试检索关联的对象时，问题就开始了。例如，当我调用@channel.get :categories时，我收到以下错误：

Mysql2::Error: Table 'ems_development.categories_channels' doesn't exist: 
SELECT `ems_categories`.* 
FROM `ems_categories` 
INNER JOIN `categories_channels` 
ON `ems_categories`.`id` = `categories_channels`.`category_id` 
WHERE `categories_channels`.`channel_id` = 1

正如你可以看到它缺少链接表上的isolate_namespace值，因为它应该查找表ems_categories_channels上的关联而不是categories_channels

任何人都有类似的问题，或者我错过了什么？

Answer 1

您可以显式设置连接表名称（per the documentation）。

  module Ems
    class Channel < ActiveRecord::Base
      has_and_belongs_to_many :categories, :join_table => 'ems_categories_channels'
    end
  end

  module Ems
    class Category < ActiveRecord::Base
      has_and_belongs_to_many :channels, :join_table => 'ems_categories_channels'
    end
  end

HABTM链接表未在可安装引擎中采用isolate_namespace值

1 个答案: