From: Salai Khine <sayakyi@...>
Date: 2008-01-04T03:52:04+09:00
Subject: Re: same Methode name but different Parameter

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Dear all,

Thankyou very much. We have finally solve problem like below. I think it is
not the best way.


class Euro

 def Euro.new_from_cent_only (cent)
    @cent = cent
  end

  def Euro.new_from_euro_cent (euro,cent)
    @cent = (euro * 100) + cent
  end

  def Euro.new_from_internal_value (an_internal_value)
    Euro.new_from_cent_only(an_internal_value)
  end
end

test1 = Euro.new_from_cent_only(10)
test2 = Euro.new_from_euro_cent(11,20)
test3 = Euro.new_from_internal_value(200)
test4 = Euro.new_from_internal_value(test3)
test5 = Euro.new_from_internal_value(200)

puts test1
puts test2 === test3
puts test3 === test5   <---- true
puts test4.object_id
puts test5.object_id


now, we have another problem. How can we test .. that
test3
test5
have differents object. ???



regards,

salai.
(Ruby Newbie)



On Jan 3, 2008 5:43 PM, Rick DeNatale <rick.denatale@gmail.com> wrote:

> On Jan 3, 2008 11:16 AM, Trans <transfire@gmail.com> wrote:
> >
> >
> > On Jan 3, 10:53 am, "Salai Khine" <saya...@gmail.com> wrote:
> > > Dear all,
> > >
> > > can i use in Ruby the *same Methode name but different Parameter*??
> > >
> > > like
> > >
> > > def new (cent)
> > >
> > > end
> > >
> > > def new(euro,cent)
> > >
> > > end.
> >
> >   def new(*args)
> >     euro, cent = *args
> >     ...
>
> Well, this didn't really answer the OPs question, and is a bit misleading.
>
> calling this with one argument will set euro to ni, and cent to the
> argument, which probably isn't what's looked for.
>
> Answering more directly, no Ruby methods are named only by the name,
> and there's no notion of overloading with different parameter types.
>
> First an aside, since you named this method new, I'm guessing that you
> are talking about creating a new object, this is (probably) another
> difference between Ruby and whatever language you have used before.
> In ruby the new method is almost never overriden (and it's a class
> method anyway so it would be def self.new;end).  Instead new objects
> are intialized through an instance method called initialize.
>
> Okay, that said there are various techniques to allow for some
> variation in parameters to a method.
>
> One is the use of a final argument prefixed by * this collects any
> arguments passed left over after any prior arguments are satisfied to
> an array.  So let's say you were doing a class representing Money
> valuated in Euros, and that you wanted EuroMoney.new(10) to create an
> object containing 10 Euro cents, and EuroMoney.new(1,50) to represent
> 1 and 1/2 Euros.  You could do this with something like
>
> class EuroMoney
>    def initialize(*args)
>          raise ArgumentError unless (1..2).include?(args.length)
>          @cents = args.last
>           if args.length > 1
>               @euros = args.first
>           else
>               @euros = 0
>           end
>      end
> end
>
> Now lets' say instead we want to be more flexible and have a money
> class which has both a value and a currency, and you want to specify a
> unit amount, and a currency with a default.  There are at least two
> ways to do this:
>
> 1)  currency argument with default value:
>
>   class Money
>        def initialize(value, currency = :euros)
>              @value, @currency = value, currency
>        end
>    end
>
> So 1.50 Euros could be created either with:
>
>      Money.new(150)
> or
>     Money.new(150, :euros)
>
> and the equivalent <G> in US Dollars would be:
>
>     Money.new(1500, :"US$")
>
> 2) use a hash argument to get the equivalent of keyword arguments
>
>    class Money
>         def initialize(&args={})
>               args = {:currency => :euros}.merge args  # this
> provides a default for currency
>               @currency = args[:currency]
>               @value = args[:value]
>          end
>     end
>
> A formal parameter with an & prefix is a hash.
>
> So we would have
>
>   Money.new(:value => 150)
>   Money.new(:currency => :euros, :value => 150)
> and
>   Money.new(:currency => :"US$", :value => 1500)
>
> as the equivalents to the previous examples.
>
> The second approach is probably overkill, on the other hand, with some
> more coding, one could use it to model more general concepts of money
> with more code in the initialize method and support things like:
>
>   Money.new(:currency => :old_imperial_english, :shillings => 10, :pounds
> => 5)
>
> which would compute the unit value based on the components in a flexible
> manner.
>
> --
> Rick DeNatale
>
> My blog on Ruby
> http://talklikeaduck.denhaven2.com/
>
>

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