This blog is part of our Ruby 2.4 series.

Ruby has many ways to match with a regular expression.

Regexp#===

It returns true/false and sets the $~ global variable.

/stat/ === "case statements"
#=> true
$~
#=> #<MatchData "stat">

Regexp#=~

It returns integer position it matched or nil if no match. It also sets the $~ global variable.

/stat/ =~ "case statements"
#=> 5
$~
#=> #<MatchData "stat">

Regexp#match

It returns match data and also sets the $~ global variable.

/stat/.match("case statements")
#=> #<MatchData "stat">
$~
#=> #<MatchData "stat">

Ruby 2.4 adds Regexp#match?

This new method just returns true/false and does not set any global variables.

/case/.match?("case statements")
#=> true

So Regexp#match? is good option when we are only concerned with the fact that regex matches or not.

Regexp#match? is also faster than its counterparts as it reduces object allocation by not creating a back reference and changing $~.

require 'benchmark/ips'

Benchmark.ips do |bench|

  EMAIL_ADDR = 'disposable.style.email.with+symbol@example.com'
  EMAIL_REGEXP_DEVISE = /\A[^@\s]+@([^@\s]+\.)+[^@\W]+\z/

  bench.report('Regexp#===') do
    EMAIL_REGEXP_DEVISE === EMAIL_ADDR
  end

  bench.report('Regexp#=~') do
    EMAIL_REGEXP_DEVISE =~ EMAIL_ADDR
  end

  bench.report('Regexp#match') do
    EMAIL_REGEXP_DEVISE.match(EMAIL_ADDR)
  end

  bench.report('Regexp#match?') do
    EMAIL_REGEXP_DEVISE.match?(EMAIL_ADDR)
  end

  bench.compare!
end

#=> Warming up --------------------------------------
#=>          Regexp#===   103.876k i/100ms
#=>           Regexp#=~   105.843k i/100ms
#=>        Regexp#match    58.980k i/100ms
#=>       Regexp#match?   107.287k i/100ms
#=> Calculating -------------------------------------
#=>          Regexp#===      1.335M (± 9.5%) i/s -      6.648M in   5.038568s
#=>           Regexp#=~      1.369M (± 6.7%) i/s -      6.880M in   5.049481s
#=>        Regexp#match    709.152k (± 5.4%) i/s -      3.539M in   5.005514s
#=>       Regexp#match?      1.543M (± 4.6%) i/s -      7.725M in   5.018696s
#=>
#=> Comparison:
#=>       Regexp#match?:  1542589.9 i/s
#=>           Regexp#=~:  1369421.3 i/s - 1.13x  slower
#=>          Regexp#===:  1335450.3 i/s - 1.16x  slower
#=>        Regexp#match:   709151.7 i/s - 2.18x  slower