In Ruby, you check with nil? if an object is nil:
article = nil
article.nil? # => true
empty? checks if an element - like a string or an array f.e. - is empty:
# Array
[].empty? #=> true
# String
"".empty? #=> true
Rails adds the method blank? to the Object class:
An object is blank if it‘s false, empty, or a whitespace string. For example, "", " ", nil, [], and {} are blank.
This simplifies
if !address.nil? && !address.empty?
to
if !address.blank?
.nil?
- It is Ruby method
- It can be used on any object and is true if the object is nil.
- "Only the object nil responds true to nil?" - RailsAPI
nil.nil? = true
anthing_else.nil? = false
a = nil
a.nil? = true
“”.nil = false
.empty?
- It is Ruby method
- can be used on strings, arrays and hashes and returns true if:
- String length == 0
- Array length == 0
- Hash length == 0
- Running .empty? on something that is nil will throw a NoMethodError
"".empty = true
" ".empty? = false
.blank?
- It is Rails method
- operate on any object as well as work like .empty? on strings, arrays and hashes.
nil.blank? = true
[].blank? = true
{}.blank? = true
"".blank? = true
5.blank? == false
- It also evaluates true on strings which are non-empty but contain only whitespace:
" ".blank? == true" ".empty? == false
Quick tip: !obj.blank? == obj.present?
activesupport/lib/active_support/core_ext/object/blank.rb, line 17 # (Ruby 1.9)
def present?
!blank?
end