module Complaint
def gripe
voice('A')
end
def faint_praise
voice('B')
end
def voice(complaint_text)
raise NotImplementedError,
"#{self.class} included the Complaint module but didn't define voice!"
end
end
class MyComplaint
include Complaint
end
MyComplaint.new.gripe
# NotImplementedError: MyComplaint included the Complaint module
# but didn't define voice!
|