How to match all occurrences of a regex
RubyRegexRuby Problem Overview
Is there a quick way to find every match of a regular expression in Ruby? I've looked through the Regex object in the Ruby STL and searched on Google to no avail.
Ruby Solutions
Solution 1 - Ruby
Using scan
should do the trick:
string.scan(/regex/)
Solution 2 - Ruby
To find all the matching strings, use String's scan
method.
str = "A 54mpl3 string w1th 7 numb3rs scatter36 ar0und"
str.scan(/\d+/)
#=> ["54", "3", "1", "7", "3", "36", "0"]
If you want, MatchData
, which is the type of the object returned by the Regexp match
method, use:
str.to_enum(:scan, /\d+/).map { Regexp.last_match }
#=> [#<MatchData "54">, #<MatchData "3">, #<MatchData "1">, #<MatchData "7">, #<MatchData "3">, #<MatchData "36">, #<MatchData "0">]
The benefit of using MatchData
is that you can use methods like offset
:
match_datas = str.to_enum(:scan, /\d+/).map { Regexp.last_match }
match_datas[0].offset(0)
#=> [2, 4]
match_datas[1].offset(0)
#=> [7, 8]
See these questions if you'd like to know more:
- "https://stackoverflow.com/questions/6804557/how-do-i-get-the-match-data-for-all-occurrences-of-a-ruby-regular-expression-in?lq=1"
- "https://stackoverflow.com/questions/19596382/ruby-regular-expression-matching-enumerator-with-named-capture-support?lq=1"
- "https://stackoverflow.com/questions/17185943/how-to-find-out-the-starting-point-for-each-match-in-ruby?lq=1"
Reading about special variables $&
, $'
, $1
, $2
in Ruby will be helpful too.
Solution 3 - Ruby
if you have a regexp with groups:
str="A 54mpl3 string w1th 7 numbers scatter3r ar0und"
re=/(\d+)[m-t]/
you can use String's scan
method to find matching groups:
str.scan re
#> [["54"], ["1"], ["3"]]
To find the matching pattern:
str.to_enum(:scan,re).map {$&}
#> ["54m", "1t", "3r"]
Solution 4 - Ruby
You can use string.scan(your_regex).flatten
. If your regex contains groups, it will return in a single plain array.
string = "A 54mpl3 string w1th 7 numbers scatter3r ar0und"
your_regex = /(\d+)[m-t]/
string.scan(your_regex).flatten
=> ["54", "1", "3"]
Regex can be a named group as well.
string = 'group_photo.jpg'
regex = /\A(?<name>.*)\.(?<ext>.*)\z/
string.scan(regex).flatten
You can also use gsub
, it's just one more way if you want MatchData.
str.gsub(/\d/).map{ Regexp.last_match }
Solution 5 - Ruby
If you have capture groups ()
inside the regex for other purposes, the proposed solutions with String#scan
and String#match
are problematic:
String#scan
only get what is inside the capture groups;String#match
only get the first match, rejecting all the others;String#matches
(proposed function) get all the matches.
On this case, we need a solution to match the regex without considering the capture groups.
String#matches
With the Refinements you can monkey patch the String
class, implement the String#matches
and this method will be available inside the scope of the class that is using the refinement. It is an incredible way to Monkey Patch classes on Ruby.
Setup
/lib/refinements/string_matches.rb
# This module add a String refinement to enable multiple String#match()s
# 1. `String#scan` only get what is inside the capture groups (inside the parens)
# 2. `String#match` only get the first match
# 3. `String#matches` (proposed function) get all the matches
module StringMatches
refine String do
def matches(regex)
scan(/(?<matching>#{regex})/).flatten
end
end
end
Used: named capture groups
Usage
rails c
> require 'refinements/string_matches'
> using StringMatches
> 'function(1, 2, 3) + function(4, 5, 6)'.matches(/function\((\d), (\d), (\d)\)/)
=> ["function(1, 2, 3)", "function(4, 5, 6)"]
> 'function(1, 2, 3) + function(4, 5, 6)'.scan(/function\((\d), (\d), (\d)\)/)
=> [["1", "2", "3"], ["4", "5", "6"]]
> 'function(1, 2, 3) + function(4, 5, 6)'.match(/function\((\d), (\d), (\d)\)/)[0]
=> "function(1, 2, 3)"