Ruby 3.1 adds MatchData#match & MatchData#match_length

Ruby 3.1 introduces the MatchData#match & MatchData#match_length methods which returns the substring matched against a regular expression & it's length respectively.

=> str = "Ruby 3.1 introduces MatchData#match method"
=>  m = /(?<lang>\S+)(\s)(?<version>[\d\.]+)/.match(str)
=> #<MatchData "Ruby 3.1" lang:"Ruby" version:"3.1">

Before Ruby 3.1

We have MatchData#[] method to access all the substring groups which are matched. We can access either a single match or multiple matches by giving a single index or range of indexes respectively using MatchData#[] method.

=> m[:lang]
=> "Ruby"

=> m[1]
=> "Ruby"
=> m[:version]
=> "3.1"

=> m[0..2]
=> ["Ruby 3.1", "Ruby", "3.1"]

=> m[1..2]
=> ["Ruby", "3.1"]


=> m[0].length
=> 8

After Ruby 3.1

We have two new methods now to access the match data & it's length. The MatchData#match & MatchData#match_length methods accepts either an index or a symbol as an argument to return the match data & it's length.

=> m.match(0)
=> "Ruby 3.1"

=> m.match(:version)
=> "3.1"

=> m.match(3)
=> nil

=> m.match_length(0)
=> 8

=> m.match_length(:version)
=> 3

=> m.match_length(3)
=> nil

Please note that MatchData#match is not same as MatchData#[] method. The later accepts an optional length or range as an argument to return the matched data but the former doesn't accept it, instead it allows only a single index or symbol as argument.

Here's the relevant pull request and feature discussion for this change.