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clark1231
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A concise explanation of nil v. empty v. blank in Ruby on Rails

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.nil?

can be used on any object and is true if the object is nil

.empty?

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

blank?()

An object is blank if it’s false, empty, or a whitespace string. For example, “”, “ ”, nil, [], and {} are all blank.

This simplifies:

if address.nil? || address.empty?

…to:

if address.blank?

That is where .blank? comes in. It is implemented by Rails and will 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

.blank? also evaluates true on strings which are non-empty but contain only whitespace.

"  ".blank? == true
"  ".empty? == false

 

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