class User
    attr_reader :name

    def initialize(name)
        @name = name
    end
end
# => :initialize

class AdminUser < User
    def is_admin?
        true
    end
end
# => :is_admin?

user = AdminUser.new("John")
# => #<AdminUser:0x007fe5a9943b80 @name="John">

user.name
# => "John"

user.is_admin?
# => true