block_conf.rb

class BlockConf
  CONF_NAMES = [:id, :pw]
  CONF_NAMES.each do |name|
    define_method name { |v| @conf[name] = v }
  end

  def self.configure &blk
    self.new &blk
  end

  attr_reader :conf

  def initialize opts={}, &blk
    @conf = opts
    instance_eval &blk unless blk.nil?
  end
end

bc = BlockConf.configure do
  id 'foooo'
  pw 'barrr'
end

puts bc.conf[:id] #=> foooo
puts bc.conf[:pw] #=> barrr

bc2 = BlockConf.new id:'barrr', pw:'bazzz'

puts bc2.conf[:id] #=> barrr
puts bc2.conf[:pw] #=> bazzz