Rails Foreign key

Posted by On 11月 11, 2014 0 Comment

Foreign key

In rails, has_many, belongs_to can express 1:many relationship, but it doesn’t include foreign key in database.
foreigner(package) can introduce foreign key to rails database.

Change gem file

gem 'foreigner', '~> 1.6.1'

Please check latest version of foreigner

Install

bundle install

Table

members 1 : many events
We manage member event in table
members

id                integer
email             string
email_index_for   string
family_name       string
last_name         string

events

id                integer
member_id         integer  (foreign key)
type              string
date              datetime

Model

rails g model member
rails g model event

Migration Script

members



class CreateMembers < ActiveRecord::Migration
  def change
    create_table :events do |t|
       t.string :email
       t.string :email_index_for
       t.string :family_name
       t.string :last_name
    end
  end
end
[/ruby]

events




class CreateEvents < ActiveRecord::Migration
  def change
    create_table :events do |t|
      t.references :member, null: false   # foreign key
      t.string :type, null: false
      t.datetime :date
    end
     
    add_foreign_key :events, :members   # members
  end
end
[/ruby]




Model


Member




class Member < ActiveRecord::Base
  has_many :events, dependent: :destroy
end
[/ruby]
Events




class Event < ActiveRecord::Base
  belongs_to :member, foreign_key: 'member_id'
end
[/ruby]

Destroy operation :destroy, :delete_all, :nullify
foreign_key option   :  with _id




  					

 			 
	
			 
					   					

										

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