From: Robert Klemme <shortcutter@...>
Date: 2012-08-03T01:14:27+09:00
Subject: Re: Supporting multiple versions of an API

On Thu, Aug 2, 2012 at 4:47 PM, Intransition <transfire@gmail.com> wrote:

> Yes, that's the traditional factory approach. I actually would not want to
> use "MainFactory", as don't want it to be explicit. But it occurs to me that
> I could have redefined `Main.new` as a factory method and done it that way.
> And the more I think about it the more that seems like a better approach. It
> would work well for Main as well as other classes within it.

It seems that in your case the caller decides on the version.  Is that correct?

What about this?

file mylib.rb:

module MyLib
  # manual
  autoload :V0 'mylib/v0'
  autoload :V1 'mylib/v1'

  # generated
  %w{V0 V1}.each do |ver|
    autoload ver.to_sym "mylib/#{ver.downcase}"
  end

  # the default
  Default = V1

  # to make access to the current version easy:
  def self.const_missing(c)
    Default.const_get(c)
  end
end

and in mylib/v0 etc.

module MyLib
  module V0
    class Main; end
  end
end

Usage

# current
m = MyLib::Main.new(...)

# explicit
m = MyLib::V0::Main.new(...)

The const_missing trick works only if there are no name conflicts, of course.

Kind regards

robert

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