The Difference Between nil?, empty?, and blank? in Ruby

The Difference Between nil?, empty?, and blank? in Ruby

In Ruby, you can use nil? method to check if the object is nil. However, Ruby also provides empty? and there’s a blank? method in Rails. For a Ruby (or Rails) newbie, it can get quite confusing, it certainly did for me. This post explains which method to use when. Hope it simplifies things a little.

1 min read


As expected, you can use nil? to check if an object is nil. It returns true only when the object is nil. For all other values, it returns false.

nil_object = nil
nil_object.nil?   # true

data =
data.nil?         # false


You can use this method on strings, arrays, and hashes. It returns true in the following cases:

  1. String doesn’t have any characters, i.e. str.length == 0
  2. Array doesn’t contain any elements, i.e. arr.length == 0
  3. Hash doesn’t have any key-value pairs, i.e. hash.length == 0
[].empty?         # true
''.empty?         # true
{}.empty?         # true
nil.empty?        # NoMethodError
false.empty?      # NoMethodError

It’s important to note that an object can be empty and not nil. For example:

names = []
names.empty?  # true
names.nil?    # false

If you try to call .empty? on a nil or any other object, Ruby throws NoMethodError.


# undefined method `empty?' for nil:NilClass (NoMethodError)


This is a nice syntactic sugar implemented in Rails. An object is blank if it’s nil, false, or empty. For example, nil,false, '', [], {}are all blank.

You can think of blank? as a shorthand for the following code.

!val || val.empty?

Here's how it works for various values.

nil.blank?    # true
false.blank?  # true
''.blank?     # true
[].blank?     # true
{}.blank?     # true

In addition, .blank? returns true if a string contains only whitespace characters.

"  ".blank? # true

Rails also provides present?, which is the opposite of blank?. It checks if the value is not blank.

That's a wrap. I hope you liked this article and you learned something new.

As always, if you have any questions or feedback, didn't understand something, or found a mistake, please leave a comment below or send me an email. I reply to all emails I get from developers, and I look forward to hearing from you.

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