interface_exists.markdown

interface_exists

There are no interfaces in Ruby the way there is in PHP. Ruby uses class inheritance or module mixins to specify an interface for an object. Both class and module names are constants, so we can check if either of these exist by verifying that the constant exists for the class or module name using Module.const_defined?.

{{code:php interface Carnivore {}

$exists = interface_exists('Carnivore');
var_export($exists);
// => true

}}

{{code:ruby class Dinosaur; end module Carnivore; end

p Module.const_defined?("Dinosaur")  # => true
p Module.const_defined?("Carnivore") # => true

}}

{{related: classobj/class_exists }}