Ruby : nil? or empty?

21 Aug 2013

Consider you wanna make sure a string is not empty as well as not nil. If you are using rails you have a blank? method to do it. but what if you are not on rails?

As usual you will write a method something like

def is_nil_or_empty? value
  value.empty? || value.nil? 

But this will through error undefined method empty?’ for nil:NilClass when you pass a nil to this method, since nil doesn’t have a method called empty?.

So I recommend you to test nil? first, like

def is_nil_or_empty? value
  value.nil? || value.empty?

So value.nil? will return true and ruby won’t check the second part since ruby uses Short Circuit Evaluation

You can also convert the value to string before checking empty, so that you don’t wanna always follow this order.

def is_nil_or_empty? value

This will work since nil.to_s will return an empty string.

If you pass false as boolean this method will return false, since "false".empty? will be false. If you are expecting other datatypes to this method then you will definity need more logic.

Happy coding. ;)

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