I want to share a method amongst all Ruby's data object classes. That is to say the following classes:

• Hash
• String
• Number
• Array

Firstly, any classes I've missed out?

Secondly, how can I share my_method amongst all classes at once?

class Hash
    def my_method
       "hi"
    end
end

class String
    def my_method
       "hi"
    end
end

class Number
    def my_method
       "hi"
    end
end

class Array
    def my_method
       "hi"
    end
end