ActiveRecord::Relationにおける present? exists? blank? empty?

結論

• 条件に合致するレコードが１件以上存在するかどうかを確認したい場合
  • exists?メソッドを使う
• 条件に合致するレコードが１件も存在しないかどうかを確認したい場合
  • empty?メソッドを使う

使用データ

irb(main):001> ExternalUser.all
  ExternalUser Load (2.1ms)  SELECT `external_users`.* FROM `external_users`
=>
[#<ExternalUser:0x0000000109a00000
  id: 1,
  name: "external_user_1",
  email: "[e-mail]",
  created_at: Tue, 16 Apr 2024 16:30:12.429205000 JST +09:00,
  updated_at: Tue, 16 Apr 2024 16:30:12.429205000 JST +09:00>]

実行結果

present?

irb(main):001> ExternalUser.all.present?
  TRANSACTION (0.1ms)  BEGIN
  ExternalUser Load (1.5ms)  SELECT `external_users`.* FROM `external_users`
=> true

exists?

irb(main):001> ExternalUser.all.exists?
  ExternalUser Exists? (0.7ms)  SELECT 1 AS one FROM `external_users` LIMIT 1
=> true

blank?

irb(main):001> ExternalUser.all.blank?
  ExternalUser Load (1.2ms)  SELECT `external_users`.* FROM `external_users`
=> false

empty?

irb(main):001> SESEvent.all.empty?
  SESEvent Exists? (1.1ms)  SELECT 1 AS one FROM `ses_events` LIMIT 1
=> true