*scratch*.rb

require "benchmark"

class KWBM
  attr_reader :foo, :baz
  def initialize(foo: "bar", baz: "biz")
    @foo = foo
    @baz = baz
  end
  
  def call
    [foo, baz].join
  end
end

class ArgBM
  attr_reader :foo, :baz
  def initialize(args={})
    @foo = args.fetch(:foo, "bar")
    @baz = args.fetch(:baz, "biz")
  end

  def call
    [foo, baz].join
  end
end

n = 1000000
rep=Benchmark.bm do |x| # !> assigned but unused variable - rep
  x.report do
    n.times do
      KWBM.new.call
    end
  end
  x.report do
    n.times do
      ArgBM.new.call
    end
  end
end

# >>        user     system      total        real
# >>    0.970000   0.000000   0.970000 (  0.963902)
# >>    1.010000   0.000000   1.010000 (  1.014589)