Question

I’m a newbie to ruby, I want to know if I can use just one line to do the job.

Take the ‘search’ of this site for example. When user typed [ruby] regex, I can use following code to get the tag and keyword

'[ruby] regex' =~ /\[(.*?)\](.*)/
tag, keyword = $1, $2

Can we write it just in one line?

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UPDATE

Thank you so much! May I make it harder and more interesting, that the input may contains more than one tags, like:

[ruby] [regex] [rails] one line

Is it possible to use one line code to get the tags array and the keyword? I tried, but failed.

Answer 1

You need the Regexp#match method. If you write /\[(.*?)\](.*)/.match('[ruby] regex'), this will return a MatchData object. If we call that object matches, then, among other things:

• matches[0] returns the whole matched string.
• matches[n] returns the nth capturing group ($n).
• matches.to_a returns an array consisting of matches[0] through matches[N].
• matches.captures returns an array consisting of just the capturing group (matches[1] through matches[N]).
• matches.pre_match returns everything before the matched string.
• matches.post_match returns everything after the matched string.

There are more methods, which correspond to other special variables, etc.; you can check MatchData‘s docs for more. Thus, in this specific case, all you need to write is

tag, keyword = /\[(.*?)\](.*)/.match('[ruby] regex').captures

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Edit 1: Alright, for your harder task, you’re going to instead want the String#scan method, which @Theo used; however, we’re going to use a different regex. The following code should work:

# You could inline the regex, but comments would probably be nice.
tag_and_text = / \[([^\]]*)\] # Match a bracket-delimited tag,
                 \s*          # ignore spaces,
                 ([^\[]*) /x  # and match non-tag search text.
input        = '[ruby] [regex] [rails] one line [foo] [bar] baz'
tags, texts  = input.scan(tag_and_text).transpose

The input.scan(tag_and_text) will return a list of tag–search-text pairs:

[ ["ruby", ""], ["regex", ""], ["rails", "one line "]
, ["foo", ""], ["bar", "baz"] ]

The transpose call flips that, so that you have a pair consisting of a tag list and a search-text list:

[["ruby", "regex", "rails", "foo", "bar"], ["", "", "one line ", "", "baz"]]

You can then do whatever you want with the results. I might suggest, for instance

search_str = texts.join(' ').strip.gsub(/\s+/, ' ')

This will concatenate the search snippets with single spaces, get rid of leading and trailing whitespace, and replace runs of multiple spaces with a single space.