Regex with named capture groups getting all matches in Ruby

Question

I have a string:

s=\"123--abc,123--abc,123--abc\"

I tried using Ruby 1.9\'s new feature \"named groups\" to fetch all named group info:

Answer 1

You can extract the used variables from the regexp using names method. So what I did is, I used regular scan method to get the matches, then zipped names and every match to create a Hash.

class String
  def scan2(regexp)
    names = regexp.names
    scan(regexp).collect do |match|
      Hash[names.zip(match)]
    end
  end
end

Usage:

>> "aaa http://www.google.com.tr aaa https://www.yahoo.com.tr ffffd".scan2 /(?<url>(?<protocol>https?):\/\/[\S]+)/
=> [{"url"=>"http://www.google.com.tr", "protocol"=>"http"}, {"url"=>"https://www.yahoo.com.tr", "protocol"=>"https"}]

Answer 2

Named captures are suitable only for one matching result.
Ruby's analogue of findall is String#scan. You can either use scan result as an array, or pass a block to it:

irb> s = "123--abc,123--abc,123--abc"
=> "123--abc,123--abc,123--abc"

irb> s.scan(/(\d*)--([a-z]*)/)
=> [["123", "abc"], ["123", "abc"], ["123", "abc"]]

irb> s.scan(/(\d*)--([a-z]*)/) do |number, chars|
irb*     p [number,chars]
irb> end
["123", "abc"]
["123", "abc"]
["123", "abc"]
=> "123--abc,123--abc,123--abc"

Answer 3

I needed something similar recently. This should work like String#scan, but return an array of MatchData objects instead.

class String
  # This method will return an array of MatchData's rather than the
  # array of strings returned by the vanilla `scan`.
  def match_all(regex)
    match_str = self
    match_datas = []
    while match_str.length > 0 do 
      md = match_str.match(regex)
      break unless md
      match_datas << md
      match_str = md.post_match
    end
    return match_datas
  end
end

Running your sample data in the REPL results in the following:

> "123--abc,123--abc,123--abc".match_all(/(?<number>\d*)--(?<chars>[a-z]*)/)
=> [#<MatchData "123--abc" number:"123" chars:"abc">,
    #<MatchData "123--abc" number:"123" chars:"abc">,
    #<MatchData "123--abc" number:"123" chars:"abc">]

You may also find my test code useful:

describe String do
  describe :match_all do
    it "it works like scan, but uses MatchData objects instead of arrays and strings" do
      mds = "ABC-123, DEF-456, GHI-098".match_all(/(?<word>[A-Z]+)-(?<number>[0-9]+)/)
      mds[0][:word].should   == "ABC"
      mds[0][:number].should == "123"
      mds[1][:word].should   == "DEF"
      mds[1][:number].should == "456"
      mds[2][:word].should   == "GHI"
      mds[2][:number].should == "098"
    end
  end
end

Answer 4

Piggybacking off of Mark Hubbart's answer, I added the following monkey-patch:

class ::Regexp
  def match_all(str)
    matches = []
    str.scan(self) { matches << $~ }

    matches
  end
end

which can be used as /(?<letter>\w)/.match_all('word'), and returns:

[#<MatchData "w" letter:"w">, #<MatchData "o" letter:"o">, #<MatchData "r" letter:"r">, #<MatchData "d" letter:"d">]

This relies on, as others have said, the use of $~ in the scan block for the match data.