ActiveRecord Associations(1) - RORLab Season 3-7

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1. Active Record Associations (1) Ror lab. season 3 - the 7th round - May 24, 2013 ChangHoon Jeong(@seapy)
2. No Associations To add an order To delete a customer
3. The Reason why we should use Active Record Associations • Automation of connecting btw models • Automatic assignment of foreign key
4. Using Active Record Associations customer order customer_id id id id parent obj. child obj. Active Record Assocation Primary & Foreign Keys
5. With Associations To add an order To delete a customer
6. Associations Parent Class Parent Class Parent Class Child Class 1 : 1 has_one has_one has_one belongs_to 1 : 1 has_one, :through has_one, :through has_one, :through belongs_to 1 : n has_many has_many has_many belongs_to n : m A has_many has_many belongs_to n : m A has_many B, :through has_many B, :through belongs_to n : m B has_many has_many belongs_to n : m B has_many A, :through has_many A, :through belongs_to n : m A / B A / B has_and_belongs_to_many has_and_belongs_to_many C
7. belongs_to vs has_one • “belongs_to” model has a foreign key • dependent upon the actual meaning of data
8. has_many :through vs has_and_belongs_to_many ๏ has_many - validations, callbacks, or extra attributes ๏ has_and_belongs_to_many - no need for additional functionalities - should create a “join” table in the DB.
9. Join Table HABTM • Default join table btw Customer & Order models : custormers_orders • Otherwise, :join_table => “join_table_name”
10. Join Table HABTM no need for join model
11. 감사합니다.