From: Robert Dober <robert.dober@...>
Date: 2008-07-24T02:25:38+09:00
Subject: Re: multiple constructors?

On Wed, Jul 23, 2008 at 7:09 PM, aidy <aidy.lewis@googlemail.com> wrote:
> Hi,
>
> Is it possible to use multiple constructors in Ruby?
>
> class SQLServerConnection
>
>  def initialize(server_name, db)
>
>  end
>
>  def initialize(server_name, db, user_name, password)
>
>  end
> end
>
> Thank You
>
> Aidy
>
>

First of all initialize is not a constructor but an initializer,
behind the scenes the following happenes

class Object
   def self.new *args, &blk
        o = allocate
        o.send :initialize, *args, &blk # this because #initialize is
*always* private
        o
   end
end

As you can see #initialize is an instance method and #new is a
singleton (or class) method.

Secondly, and that holds for all methods, #initialize is only an
example, you cannot "overload" method definitions but simulate that
behavior, in your case I would do the following

class SQLServerConnection

   private

   def initialize *args
      case args.size
      when 2
         init_name_db *args
      when 4
        init_user_pw *args
     else
      error
    end
end

   def init_name_db server_name, db
    ...
   end

  def init_user_pwd server_name, db, user, pwd
   ...
  end
end

HTH
Robert




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