How to set up custom string foreign key in Rails 4?

Question

How to set up associations to properly configure has_one with string foreign_key?

class Pharmaceutic < ActiveRecord::Base has_one :pharmaceutic_group, foreign_key: "code" end class PharmaceuticGroup < ActiveRecord::Base belongs_to :pharmaceutic, primary_key: 'code' end >> Pharmaceutic.last.pharmaceutic_group Pharmaceutic Load (0.3ms) SELECT `pharmaceutics`.* FROM `pharmaceutics` ORDER BY `pharmaceutics`.`id` DESC LIMIT 1 PharmaceuticGroup Load (0.3ms) SELECT `pharmaceutic_groups`.* FROM `pharmaceutic_groups` WHERE `pharmaceutic_groups`.`code` = 2 ORDER BY `pharmaceutic_groups`.`id` ASC LIMIT 1 => nil >> Pharmaceutic => Pharmaceutic(id: integer, package_type: integer, group_code: string) >> PharmaceuticGroup => PharmaceuticGroup(id: integer, code: string, name: string) 

For example, when: The pharmacist has group_code: aaa and PharmaceuticGroup has the code: aaa I would like to receive Pharmaceutic.last.pharmaceutic_group.name => 'AAA group name'

Answer 1

I think you should use Pharmaceutic belongs_to :pharmaceutic_group and PharmaceuticGroup has_many :pharmaceutics , for example:

 class Pharmaceutic < ActiveRecord::Base belongs_to :pharmaceutic_group, foreign_key: :group_code, primary_key: :code end class PharmaceuticGroup < ActiveRecord::Base has_many :pharmaceutics, foreign_key: :group_code, primary_key: :code end