From: ThoML <micathom@...>
Date: 2008-02-13T06:30:05+09:00
Subject: Re: Subclassing Integer; solved!

> > Year.new(2008).class # => Fixnum
> > Year.new(2008) == 2008 # => true
>
> That's exactly what I want.

The latter gives false with ruby19 though. Also it seems impossible to
define a method in Year.

    class Year < Integer
        def foo
            self * 2000
        end
    end
    Year.new(2008).foo
    # NoMethodError: undefined method `foo' for 2008:Fixnum

Also, I don't quite understand the hack with inherited() since it
doesn't do anything. The reason why the class() method returns
'Fixnum' is not because of the inheritance but because of
#method_missing. A IMHO slightly more accessible/"traditional" way to
achieve the same would be:

    class Year < BasicObject
        def initialize(value)
            @value = value
        end

        def foo
            @value * 2000
        end

        def ==(other)
            @value == other
        end

        def respond_to?
            @value.respond_to?
        end

        private
        def method_missing(meth, *args, &block)
            @value.send meth, *args, &block
        end
    end

    Year.new(2008).class
    # => Fixnum
    Year.new(2008).foo
    # => 4016000
    Year.new(2008) == 2008
    # => true
    Year.new(2008).class.superclass
    # => Integer

If you define #method_missing, you'll also have to define respond_to?.
It seems also necessary to define #== and a few other methods:

    irb(main):001:0> BasicObject.instance_methods
    => [:==, :equal?, :"!", :"!=", :__send__]

Regards,
Thomas.