Rails - Differences between nil?, empty?, blank?, and present?

Index

• nil?
• empty?
• blank?
• present?
• Recap

nil?

#nil? is a Ruby method on the Object class. Since all classes inherit from this class, #nil? can be used on any object.

nil.nil?
=> true

true.nil?
=> false

5.nil?
=> false

"".nil?
=> false

[].nil?
=> false

empty?

#empty? is a Ruby method that can be used on strings, arrays, hashes and sets.

strings

"".empty?
=> true

" ".empty?
=> false

"\t\n".empty?
=> false

arrays, hashes and sets

It returns true if they have no elements

[].empty?
=> true

{}.empty?
=> true

require 'set'
Set.new.empty?
=> true

blank?

#blank? is a Rails method. It operates on any object.

strings

"".blank?
=> true

" ".blank?
=> true

"\n\t".blank?
=> true

arrays, hashes and sets

It works just like #empty?

present?

#present? is a Rails method. It does the opposite of what #blank? does.

Recap