Dynamic method calling in Ruby

Question

As far as I am aware there are three ways to dynamically call a method in Ruby:

Method 1:

s = SomeObject.new
method = s.method(:dynamic_method)
metho         


        

Answer 1

Here is all possible method calls:

require 'benchmark/ips'

class FooBar
  def name; end
end

el = FooBar.new

Benchmark.ips do |x|
  x.report('plain') { el.name }
  x.report('eval') { eval('el.name') }
  x.report('method call') { el.method(:name).call }
  x.report('send sym') { el.send(:name) }
  x.report('send str') { el.send('name') }
  x.compare!
end

And results are:

Warming up --------------------------------------
               plain   236.448k i/100ms
                eval    20.743k i/100ms
         method call   131.408k i/100ms
            send sym   205.491k i/100ms
            send str   168.137k i/100ms
Calculating -------------------------------------
               plain      9.150M (± 6.5%) i/s -     45.634M in   5.009566s
                eval    232.303k (± 5.4%) i/s -      1.162M in   5.015430s
         method call      2.602M (± 4.5%) i/s -     13.009M in   5.010535s
            send sym      6.729M (± 8.6%) i/s -     33.495M in   5.016481s
            send str      4.027M (± 5.7%) i/s -     20.176M in   5.027409s

Comparison:
               plain:  9149514.0 i/s
            send sym:  6729490.1 i/s - 1.36x  slower
            send str:  4026672.4 i/s - 2.27x  slower
         method call:  2601777.5 i/s - 3.52x  slower
                eval:   232302.6 i/s - 39.39x  slower

It's expected that plain call is the fastest, no any additional allocations, symbol lookups, just lookup and evaluation of method.

As for send via symbol, it is faster than via string as its much more easer to allocate memory for symbol. Once it's defined it's stored for long term in memory and there no reallocations.

The same reason can be said about method(:name) (1) it's requires to allocate memory for Proc object (2) we are calling the method in class which leads for additional method lookup which takes time too.

eval is runs interpreter so it's the heaviest.