我必须在其中拥有的habtm关系相同的命名空间两种车型。
class Resource::Item < ApplicationRecord
has_and_belongs_to_many :resource_sets, foreign_key: 'resource_item_id', class_name: 'Resource::Set', table_name: 'resource_items_sets'
end
class Resource::Set < ApplicationRecord
has_and_belongs_to_many :resource_items, foreign_key: 'resource_set_id', class_name: 'Resource::Item', table_name: 'resource_items_sets'
end
迁移已经rails g migration CreateJoinTableResourceItemsResourceSets resource_item resource_set
生成
class CreateJoinTableResourceItemsResourceSets < ActiveRecord::Migration[5.2]
def change
create_join_table :resource_items, :resource_sets do |t|
# t.index [:resource_item_id, :resource_set_id]
# t.index [:resource_set_id, :resource_item_id]
end
end
end
到目前为止,一切看起来都很好。该表resource_items_sets
正在与两列resource_item_id
和resource_set_id
创建。
这是架构
create_table "resource_items_sets", id: false, force: :cascade do |t|
t.bigint "resource_item_id", null: false
t.bigint "resource_set_id", null: false
end
创建resource_item后,我得到被预期以下。
pry(main)> Resource::Item.first.resource_sets
=> #<Resource::Set::ActiveRecord_Associations_CollectionProxy:0x3fdd08748004>
但这样做的以下抛出一个错误。我期待0
。
pry(main)> Resource::Item.first.resource_sets.count
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR: column resource_items_sets.set_id does not exist
LINE 1: ...N "resource_items_sets" ON "resource_sets"."id" = "resource_...
^
: SELECT "resource_sets"."id" FROM "resource_sets" INNER JOIN "resource_items_sets" ON "resource_sets"."id" = "resource_items_sets"."set_id" WHERE "resource_items_sets"."resource_item_id" = $1 ORDER BY "resource_sets"."name" ASC
from /Users/username/.rvm/gems/ruby-2.6.0/gems/activerecord-5.2.2/lib/active_record/connection_adapters/postgresql_adapter.rb:677:in `async_prepare'
Caused by PG::UndefinedColumn: ERROR: column resource_items_sets.set_id does not exist
LINE 1: ...N "resource_items_sets" ON "resource_sets"."id" = "resource_...
哪里set_id
来的时候resource_set_id
已申报到处?我怎样才能解决这个问题?我想保持其命名空间都因为这样我可能会创建项目和多个命名空间设置。
非常感谢你们!
您需要设置在连接表两侧的外键,因为他们不能在你的情况来推断。
在这种情况下,正确的has_and_belongs_to_many
调用应该是这样的:
has_and_belongs_to_many :resource_items,
foreign_key: 'resource_set_id',
association_foreign_key: 'resource_item_id',
class_name: 'Resource::Item',
join_table: 'resource_items_sets'
end
和
class Resource::Item < ApplicationRecord
has_and_belongs_to_many :resource_sets,
foreign_key: 'resource_item_id',
association_foreign_key: 'resource_set_id',
class_name: 'Resource::Set',
join_table: 'resource_items_sets'
end
请注意添加association_foreign_key
选项指定连接表中的其它外键。