Selective instance eval

1_selective_instance_eval.rb

String.class_eval do
  alias_method :original_initialize, :initialize
  def initialize(*args)
    # https://www.ruby-forum.com/topic/1893190
    c = caller(0)

    case
    when c.to_s.include?('module:V1')
      instance_eval do
        def to_v1
          "v1_#{self}"
        end
      end
    when c.to_s.include?('module:V2')
      instance_eval do
        def to_v2
          "v2_#{self}"
        end
      end
    end

    original_initialize(*args)
  end
end

puts '--- V1 ---'
module V1
  puts String.new('titi').to_v1
  puts String.new('titi').to_v2
rescue => ex
  puts ex.message
end

puts '--- V2 ---'
module V2
  puts String.new('titi').to_v2
  puts String.new('titi').to_v1
rescue => ex
  puts ex.message
end

2_console.md

--- V1 ---
v1_titi
undefined method `to_v2' for "titi":String
--- V2 ---
v2_titi
undefined method `to_v1' for "titi":String