has_many：通过外键？

我已经阅读了多个有关此问题的问题，但尚未找到适合我情况的答案。

我有3个型号： Apps ， AppsGenres和Genres

以下是每个相关领域：

 Apps application_id AppsGenres genre_id application_id Genres genre_id 

这里的关键是我没有使用那些模型中的id字段。

我需要根据那些application_id和genre_id字段关联表。

这是我目前得到的，但它没有得到我需要的查询：

 class Genre  :application_id, :foreign_key => :application_id has_many :apps, :through => :apps_genres end class AppsGenre  :application_id belongs_to :genre, :foreign_key => :application_id, :primary_key => :application_id end class App  :application_id, :primary_key => :application_id has_many :genres, :through => :apps_genres end 

作为参考，这是我最终需要的查询：

 @apps = Genre.find_by_genre_id(6000).apps SELECT "apps".* FROM "apps" INNER JOIN "apps_genres" ON "apps"."application_id" = "apps_genres"."application_id" WHERE "apps_genres"."genre_id" = 6000 

Answer 1

更新试试这个：

 class App < ActiveRecord::Base has_many :apps_genres, :foreign_key => :application_id has_many :genres, :through => :apps_genres end class AppsGenre < ActiveRecord::Base belongs_to :genre, :foreign_key => :genre_id, :primary_key => :genre_id belongs_to :app, :foreign_key => :application_id, :primary_key => :application_id end class Genre < ActiveRecord::Base has_many :apps_genres, :foreign_key => :genre_id has_many :apps, :through => :apps_genres end 

有了查询：

 App.find(1).genres 

它产生：

 SELECT `genres`.* FROM `genres` INNER JOIN `apps_genres` ON `genres`.`genre_id` = `apps_genres`.`genre_id` WHERE `apps_genres`.`application_id` = 1 

并查询：

 Genre.find(1).apps 

产生：

 SELECT `apps`.* FROM `apps` INNER JOIN `apps_genres` ON `apps`.`application_id` = `apps_genres`.`application_id` WHERE `apps_genres`.`genre_id` = 1