Help us understand the problem. What is going on with this article?

Rubyのnil?とempty?とblank?の違いとpresent?

nil?はnilだけtrue、empty?よりblank?の方が幅広く使える、present?はblank?の否定

どうも、ITのんびりです

Rubyのメソッドでnil?とempty?とblank?の違いが分からなかったのでまとめました

テストコードのバリデーションで、「リクエストパラメータが空白とかnilとかの場合に、このバリデーションをかけたい!」という判定にはblank?メソッドを使うといいと思います!

nil?メソッド

nil?はnilの時だけtrue

nil.nil?
=> true

[].nil?
=> false

{}.nil?
=> false

"".nil?
=> false

false.nil?
=> false

empty?メソッド

empty?は入れ物はあるが中身がない時true

nil.empty?
=> NoMethodError: undefined method 'empty?' for nil:NilClass

[].empty?
=> true

{}.empty?
=> true

"".empty?
=> true

"       ".empty?
=> false

false.empty?
NoMethodError: undefined method `empty?' for false:FalseClass

blank?メソッド

blank?はempty?より範囲が広い

Railsでは使えるけど、rubyだけでは使えない

nil.blank?
=> true

[].blank?

=> true

{}.blank?
=> true

"".blank?
=> true

"       ".blank?
=> true

false.blank?
=> true

present?はblank?の否定

参考
http://railsdoc.com/references/blank

おわりに

最後まで読んでいただきありがとうございました。
QiitaやTwitterなどにコメントをしてもらったり、SNSでシェアしてもらえるとうれしいです!


Why do not you register as a user and use Qiita more conveniently?
  1. We will deliver articles that match you
    By following users and tags, you can catch up information on technical fields that you are interested in as a whole
  2. you can read useful information later efficiently
    By "stocking" the articles you like, you can search right away
Comments
Sign up for free and join this conversation.
If you already have a Qiita account
Why do not you register as a user and use Qiita more conveniently?
You need to log in to use this function. Qiita can be used more conveniently after logging in.
You seem to be reading articles frequently this month. Qiita can be used more conveniently after logging in.
  1. We will deliver articles that match you
    By following users and tags, you can catch up information on technical fields that you are interested in as a whole
  2. you can read useful information later efficiently
    By "stocking" the articles you like, you can search right away