Ruby/rails/db関連付け

関連付け一覧

belongs_to
has_one
has_many
has_many :through
has_one :through
has_and_belongs_to_many

belongs_to関連付けオプション

:autosave
:class_name
:counter_cache
:dependent
:foreign_key
:primary_key
:inverse_of
:polymorphic
:touch
:validate
:optional

1:n関連のデータ取得例

class Battle < ApplicationRecord
  belongs_to :user
end
class User < ApplicationRecord
  has_many :battle
end

battles = Battle.where("user_id = ?", params[:id])
battles.each do |battle|
  logger.debug("battle.user.name=#{battle.user.name}")
end

1:1関連のデータ取得例

class Supplier < ApplicationRecord
  has_one :account
end
class Account < ApplicationRecord
end

acounts = Account.all
acounts.each do |account|
  logger.debug("account.supplier.name=#{account.supplier.name}")
end

命名規則が使えない場合の1:n紐付け

battles.battle_user_idをusers.idと紐づける

class User < ApplicationRecord
  has_many :battle
end
class Battle < ApplicationRecord
  belongs_to :user
  belongs_to :battle_user, class_name: "User"
end

battles = Battle.where("user_id = ?", params[:id])
battles.each do |battle|
  logger.debug("battle.user_id=#{battle.battle_user.name}")
end

参考

公式rails関連付け：https://railsguides.jp/association_basics.html