From: botp <botpena@...>
Date: 2011-01-28T12:52:20+09:00
Subject: Re: why is overloading invalid in ruby.

On Fri, Jan 28, 2011 at 3:22 AM, Ted Flethuseo <flethuseo@gmail.com> wrote:
> I don't understand why when I try to overload I get an error. Can I
> overload somehow?

Hi Ted,

sorry no overloading in ruby. overloading gives fixed/absolute power
to compiler/interpreter. ruby is dynamic, everything can be changed at
runtime, anytime. second, ruby is oo, ojbect first progg,
polymorph-based ie.


>  def sum(x)
>    return x + 2
      ^^
lose the return, ruby does not need it here

as others have mentioned, you can use starred args and default params
to mimic overloading. if that does not fit your taste, you can use
named params or hash (it fits mine :)

the advantage of named params over static signature/position-based
param is that you have more control of your method since it is really
*the* params (wc are objects by themselves) that do the playing, not
the positioning (again, emphasizing o-o-ness). ergo,  you have better
control and you can test/debug the methods a lot better.

now if that still does not suit your taste, you can do polymorphism,
wc of course comes natural in o-o langgs.

anyway, the ff code shows how to scheme thru named parameters way,

eg,

class Summer
  def sum(opt={:none=>"none entered :)"})
    case opt.keys.sort
      when [:none]
        opt[:none]
      when [:x]
        sumx opt[:x]
      when [:x, :y]
        sumxy opt[:x], opt[:y]
      when [:x, :y, :z]
        # you can place more conditions here
        sumxyz opt[:x], opt[:y], opt[:z]
      when [:a, :x, :y, :z]
        sumxyz_xa opt[:x], opt[:y], opt[:z], opt[:a]
      else
         # you can place other conditions and methods here, do anything
    end
  end

  private

  def sumx x
    x + 2
  end

  def sumxy x,y
    x + y
  end

  def sumxyz x,y,z
    x + y + z
  end

  def sumxyz_xa x,y,z,a
    sumxyz(x,y,z) ** a
  end
end
#=> nil

s = Summer.new
#=> #<Summer:0x918e350>
puts s.sum()
none entered :)
#=> nil
puts s.sum(x:3)
5
#=> nil
# note also that the params have been disarranged to show flex
puts s.sum(x:3,y:4)
7
#=> nil
puts s.sum(z:5,x:3,y:4)
12
#=> nil
# this last sample call previous method and raises that to power :a
puts s.sum(y:4,a:6,x:3,z:5)
2985984
#=> nil

best regard -botp