Ruby one-liner to capture regular expression matches

Question

In Perl, I use the following one line statements to pull matches out of a string via regular expressions and assign them. This one finds a single match and assigns it to a string:

my $string = "the quick brown fox jumps over the lazy dog.";

my $extractString = ($string =~ m{fox (.*?) dog})[0];

Result: $extractString == 'jumps over the lazy'

And this one creates an array from multiple matches:

my $string = "the quick brown fox jumps over the lazy dog.";

my @extractArray = $string =~ m{the (.*?) fox .*?the (.*?) dog};

Result: @extractArray == ['quick brown', 'lazy']

Is there an equivalent way to create these one-liners in Ruby?

Answer 1

string = "the quick brown fox jumps over the lazy dog."

extract_string = string[/fox (.*?) dog/, 1]
# => "jumps over the lazy"

extract_array = string.scan(/the (.*?) fox .*?the (.*?) dog/).first
# => ["quick brown", "lazy"]

This approach will also return nil (instead of throwing an error) if no match is found.

extract_string = string[/MISSING_CAT (.*?) dog/, 1]
# => nil

extract_array = string.scan(/the (.*?) MISSING_CAT .*?the (.*?) dog/).first
# => nil

Answer 2

Use String#match and MatchData#[] or MatchData#captures to get matched backreferences.

s = "the quick brown fox jumps over the lazy dog."

s.match(/fox (.*?) dog/)[1]
# => "jumps over the lazy"
s.match(/fox (.*?) dog/).captures
# => ["jumps over the lazy"]

s.match(/the (.*?) fox .*?the (.*?) dog/)[1..2]
# => ["quick brown", "lazy"]
s.match(/the (.*?) fox .*?the (.*?) dog/).captures
# => ["quick brown", "lazy"]

UPDATE

To avoid undefined method [] error:

(s.match(/fox (.*?) cat/) || [])[1]
# => nil
(s.match(/the (.*?) fox .*?the (.*?) cat/) || [])[1..2]
# => nil
(s.match(/the (.*?) fox .*?the (.*?) cat/) || [])[1..-1] # instead of .captures
# => nil