Question

Can you explain why empty? and nil? methods return different results?

ruby-1.9.2-p0 > [].empty?
 => true 
ruby-1.9.2-p0 > {}.nil?
 => false 
ruby-1.9.2-p0 > {}.empty?
 => true 
ruby-1.9.2-p0 > [].empty?
 => true 
ruby-1.9.2-p0 > [].nil?
 => false 

Answer 1

I’m guessing you are coming from python? Python and other languages can be quite loose about tests for various design reasons.

Ruby takes the strict approach.

nil? is only for testing nil (no value).

empty? is testing for containers (arrays, hashes) that have nothing in them.

Search for ruby documentation on those methods. For example, here is empty for array.

You might also like this tutorial.