nil? vs empty? vs blank? in ruby

nil?

This method is available on all objects and returns true only when the object is nil.

nil.nil?               #=> true
[].nil?                #=> false
"".nil?                #=> false
1.nil?                 #=> false

empty?

This method is available on String, Array and Hash and returns true only when they are empty. Empty here means the object is not nil but does not have any value inside.

For example:

"".empty?               #=> true
[].empty?               #=> true
{}.empty?               #=> true

blank?

ℹ️ #blank? is a rails method

An object is blank if it’s false, empty, or a whitespace string.

false.blank?            #=> true
"".blank?               #=> true
"  ".blank?             #=> true
nil.blank?              #=> true
[].blank?               #=> true
{}.blank?               #=> true

Comparison

	#nil?	#empty?	#blank?
nil	true	NoMethodError	true
[]	false	true	true
{}	false	true	true
""	false	true	true
" "	false	false	true
1	false	NoMethodError	false
true	false	NoMethodError	false
false	false	NoMethodError	true