Module is_a?

modinheritance.rb

#!/usr/bin/env ruby

class A
    def initialize
        puts "Initializing an A"
        super
    end
end

module B
    def initialize
        puts "Initializing a B"
        super
    end
end

module B2
    include B

    def initialize
        puts "Initializing a B2"
        super
    end
end

class C < A
    include B2

    def initialize
        puts "Initializing a C"
        super
    end
end


obj = C.new

[ C, B, B2, A ].each do |mod|
    puts "%p is_a %p? %p" % [ obj, mod, obj.is_a?(mod) ]
end

# $ ruby ~/source/ruby/misc/modinheritance.rb 
# Initializing a C
# Initializing a B2
# Initializing a B
# Initializing an A
# #<C:0x0000010086a690> is_a C? true
# #<C:0x0000010086a690> is_a B? true
# #<C:0x0000010086a690> is_a B2? true
# #<C:0x0000010086a690> is_a A? true