Benchmark on using instance_variable_set v.s. instance_eval

bench.rb

 require 'benchmark'

  class Foo
    def bar
      true
    end
  end

  n = 1_000_000
  Benchmark.bm(30) do | b |
    b.report "instance_variable_set" do
      n.times do
        instance = Foo.new
        instance.instance_variable_set(:@baz, Hash.new)
      end
    end

    b.report "instance_eval" do
      n.times do
        instance = Foo.new
        instance.instance_eval do
          @baz = Hash.new
        end
      end
    end
  end


#                                      user     system      total        real
#  instance_variable_set           0.720000   0.000000   0.720000 (  0.715357)
#  instance_eval                   5.280000   0.000000   5.280000 (  5.284949)