Determining class of an object with case equality operator (===)

Case equality operator (or triple equals, ===) in Ruby returns true if the passed class is in the ancestors list of the passed object's class:

 1.class.ancestors # [Integer, Numeric, Object, ...] Numeric === 1 # true Object === 1 # true 

So it can be used for determining object's class:

 String === 'abc' # true 'abc'.class #=> String 

In cases above the case equality operator works like #kind_of? (or #is_a?):

 1.kind_of?(Integer) # true 1.is_a?(Numeric) # true 

The classes above has different implementations of === operator, that's why the results of comparison are different:

 String.===('abc') # the same as String === 'abc' 

Also it means that order of the arguments is important:

 1 === Integer # false