搁补颈濒蝉モデル设计ケーススタディ
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This document discusses various Rails model design patterns and ActiveRecord associations including has_one, has_many, belongs_to, has_many :through, has_and_belongs_to_many, polymorphic associations, single table inheritance, and self-joins. It provides code examples for implementing has_many :through, has_and_belongs_to_many, polymorphic associations, and single table inheritance. The document also compares when to use has_many :through vs has_and_belongs_to_many and polymorphic associations vs single table inheritance.
搁补颈濒蝉モデル设计ケーススタディ
- 6. has_many :through実装例 ./bin/rails g model Product name ./bin/rails g model Order total_price:integer ./bin/rails g model ProductOrder product:references order:references
- 7. mysql> desc product_orders; +------------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+----------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | product_id | int(11) | YES | MUL | NULL | | | order_id | int(11) | YES | MUL | NULL | | | created_at | datetime | NO | | NULL | | | updated_at | datetime | NO | | NULL | | +------------+----------+------+-----+---------+----------------+
- 8. class Product < ActiveRecord::Base has_many :product_orders has_many :orders, through: :product_orders end class ProductOrder < ActiveRecord::Base belongs_to :product belongs_to :order end Product.first.orders
- 9. has_and_belongs_to_manyの実装 例 ./bin/rails g model Article title ./bin/rails g model Tag name ./bin/rails g create_join_table_article_tag article tag
- 10. mysql> desc articles_tags; +------------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +------------+---------+------+-----+---------+-------+ | article_id | int(11) | NO | | NULL | | | tag_id | int(11) | NO | | NULL | | +------------+---------+------+-----+---------+-------+
- 11. class Article < ActiveRecord::Base has_and_belongs_to_many :tags end Article.first.tags
- 17. ポリモーフィック実装例 ./bin/rails g model Camera iso ./bin/rails g model Pc cpu ./bin/rails g model Review reviewable:references{polymorphic}:index message
- 18. mysql> desc cameras; +------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | iso | varchar(255) | YES | | NULL | | | created_at | datetime | NO | | NULL | | | updated_at | datetime | NO | | NULL | | +------------+--------------+------+-----+---------+----------------+ mysql> desc reviews; +-----------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra +-----------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | reviewable_id | int(11) | YES | | NULL | | reviewable_type | varchar(255) | YES | MUL | NULL |
- 19. class Camera < ActiveRecord::Base has_many :reviews, as: :reviewable end class Review < ActiveRecord::Base belongs_to :reviewable, polymorphic: true end
- 20. c = Camera.create(iso:3200) c.reviews.create(message: "hoge") mysql> select * from reviews; +----+---------------+-----------------+---------+---------------------+----- | id | reviewable_id | reviewable_type | message | created_at | upda +----+---------------+-----------------+---------+---------------------+----- | 1 | 1 | Camera | hoge | 2016-04-05 17:10:48 | 2016 | 2 | 1 | Pc | piyo | 2016-04-05 17:13:03 | 2016 +----+---------------+-----------------+---------+---------------------+-----
- 21. STIの実装例 ./bin/rails g model Player name goal:integer homerun:integer type ./bin/rails g model footballer --parent player ./bin/rails g model baseballer --parent player
- 22. mysql> desc players; +------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(255) | YES | | NULL | | | goal | int(11) | YES | | NULL | | | homerun | int(11) | YES | | NULL | | | type | varchar(255) | YES | | NULL | | | created_at | datetime | NO | | NULL | | | updated_at | datetime | NO | | NULL | | +------------+--------------+------+-----+---------+----------------+
- 23. class Player < ActiveRecord::Base end class Footballer < Player end
- 24. Footballer.create(name: 'hide', goal: 10) Baseballer.create(name: 'ichiro', homerun: 5) mysql> select * from players; +----+--------+------+---------+------------+---------------------+---------- | id | name | goal | homerun | type | created_at | updated_a +----+--------+------+---------+------------+---------------------+---------- | 1 | hide | 10 | NULL | Footballer | 2016-04-05 17:21:02 | 2016 | 2 | ichiro | NULL | 5 | Baseballer | 2016-04-05 17:21:28 | 2016 +----+--------+------+---------+------------+---------------------+----------