如何通过多个数据库连接创建 has_many ?
我有一个名为“master”的数据库,其中保存位置信息。这是从单独的应用程序更新的。用户可以访问许多位置,但所有其他模型都位于另一个名为“budget”的数据库中。以下是模型的设置方式。
# place.rb
class Place < ActiveRecord::Base
belongs_to :user
belongs_to :location
end
# user.rb
class User < ActiveRecord::Base
has_many :locations, :through => :places
has_many :places
end
# location.rb
class Location < ActiveRecord::Base
establish_connection "master"
has_many :places
has_many :users, :through => :places
end
当我通过 irb 运行命令时,我得到以下信息
> Location.first.places.create(:user_id => 1)
> #<Place id: 1, user_id: 1, location_id: 1, created_at: "2011-11-28 20:58:43", updated_at: "2011-11-28 20:58:43">
> Location.first.places
> [#<Place id: 1, user_id: 1, location_id: 1, created_at: "2011-11-28 20:58:43", updated_at: "2011-11-28 20:58:43">]
> Location.first.users
> [#<User id: 1, username: "toby", role: "guest", created_at: "2011-11-28 17:45:40", updated_at: "2011-11-28 17:45:40">
> User.first.locations
> Mysql2::Error: Table 'master.places' doesn't exist: SELECT `locations`.* FROM `locations` INNER JOIN `places` ON `locations`.`id` = `places`.`location_id` WHERE `places`.`user_id` = 1 ActiveRecord::StatementInvalid: Mysql2::Error: Table 'master.places' doesn't exist: SELECT `locations`.* FROM `locations` INNER JOIN `places` ON `locations`.`id` = `places`.`location_id` WHERE `places`.`user_id` = 1
我尝试将当前的 Rails env 添加到 Place 中,以尝试覆盖 place 的默认数据库,如下所示: # 地点.rb 上课地点 < ActiveRecord::Base establish_connection Rails.env belongs_to :user belongs_to :location end
#database.yml
master:
adapter: mysql2
encoding: utf8
reconnect: false
database: master
pool: 5
username: root
password:
socket: /var/run/mysqld/mysqld.sock
development:
adapter: mysql2
encoding: utf8
reconnect: false
database: budget_development
pool: 5
username: root
password:
socket: /var/run/mysqld/mysqld.sock
那没有帮助。有什么想法吗?
一位朋友帮我回答了这个问题,我想这可能对其他人有用。
class Location < ActiveRecord::Base
#establish_connection "master"
def self.table_name() "master.locations" end
has_many :places
has_many :users, :through => :places
end
答案对我有用,但我在我的关系表中使用这个版本:
self.table_name = "master.locations"
任何几年后阅读本文的人,请注意 Rails 7 已为
disable_joins: true
和 has_one
引入了显式 has_many
选项。