Benchmark local var caching vs direct method access

benchmark_local_var_vs_instance_var.rb

require 'benchmark'
require 'active_support/all'

Source = Struct.new(:value, keyword_init: true)

def local_var_test(source)
  value = source.value
  return if value.nil?
  value
end

def direct_test(source)
  return if source.value.nil?
  source.value
end

source = Source.new(value: "value")

n = 100_000
Benchmark.bmbm(15) do |x|
  x.report("local var") { n.times { local_var_test(source) } }
  x.report("direct")    { n.times { direct_test(source) } }
end

# >>                       user     system      total        real
# >> local var         0.006867   0.000004   0.006871 (  0.006869)
# >> direct            0.007748   0.000002   0.007750 (  0.007748)