From: Josh Cheek <josh.cheek@...>
Date: 2011-08-29T17:49:18+09:00
Subject: Re: String#split resets regex captures variables (Ruby 1.8.7)

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2011/8/29 Bartosz Dziewo=C5=84ski <matma.rex@gmail.com>

> I think it makes sense for $1, $2 etc to change any time a regex match
> is performed anywhere in Ruby, it might be even kind of useful in some
> perverse scenarios. That said, you shouldn't use these if you can,
> it's a Perl relic (but I admit, sometimes it's the easiest way).
>
>
I don't, that means that if you call some method, then it can implicitly an=
d
unintentionally change variables you've set, and the only way to know it is
to go digging through source code. You could empirically experiment with it=
,
but say the regex was conditionally evaluated, then you'd not know it was
used unless conditions were right, meaning it might not pop up until you
were in production.


> There are two solutions: either bind their values to another variables:
>
>  n =3D "a:c"
>  if n =3D~ /([a-z])([.:])([a-z])/
>   sep =3D $2
>  p [:first, :second].zip(n.split(sep)) | [[:separator, sep]]
>  end
>
> or use #match like a man:
>
>  n =3D "a:c"
>  if mtc =3D n.match(/([a-z])([.:])([a-z])/)
>  p [:first, :second].zip(n.split(mtc[2])) | [[:separator, mtc[2]]]
>  end
>
>
Another option, for more recent rubies, is to use named capture groups


if "a:c" =3D~ /(?<first>[a-z])(?<separator>[.:])(?<second>[a-z])/
  p $~.names.map(&:intern).zip($~.captures)
end

# >> [[:first, "a"], [:separator, ":"], [:second, "c"]]

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