ruby 方法重载

class MyClass
    def sayHello
        return "hello from MyClass"
    end
    def sayGoodbye
        return "Goodbye from MyClass"
    end
end
class MyOtherClass < MyClass
    def sayHello
        return "Hello from MyOtherClass"
    end
    def sayGoodbye    
        return super << "and also from MyOtherClass"
    end
    def to_s
        return "I am an instance of the #{self.class} class"
    end
end