From: Brian Candler <lists@...>
Date: 2012-09-03T21:27:16+09:00
Subject: Re: Extract # Number from a string

Robert Klemme wrote in post #1074406:
> On Mon, Sep 3, 2012 at 9:44 AM, Brian Candler <lists@ruby-forum.com>
> wrote:
>> if old_string =~ /#([0-9]+)/
>>   new_string = $1
>> else
>>   puts "Couldn't find it"
>> end
>
> Or use String#[]:
...
> irb(main):009:0> arr.map {|s| s[/(?<=#)\d+/]}

...although the positive lookbehind assertion (?<=...) is a somewhat 
esoteric feature of regexps. You can avoid it using the form 
String#[regexp, fixnum] to get just the captured value that you are 
interested in.

>> s = "this is a #123 string"
=> "this is a #123 string"
>> s[/#(\d+)/, 1]
=> "123"

Another option is to use String#match or Regexp#match, which return a 
MatchData object, that in turn you can query for the captures.

>> s = "this is a #123 string"
=> "this is a #123 string"
>> s.match(/#(\d+)/)
=> #<MatchData "#123" 1:"123">
>> s.match(/#(\d+)/)[1]
=> "123"
>> /#(\d+)/.match(s)[1]
=> "123"

There's certainly More Than One Way To Do It :-)

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