From: Robert Klemme <shortcutter@...>
Date: 2010-02-27T06:57:54+09:00
Subject: Re: Regex for "not matching" an unneeded prefix substring?

2010/2/26 Jet Koten <jetkoten@gmail.com>:
> Hi all,
>
> I'm new to Ruby and even newer to regex. I'm trying to write my first
> [useful] Ruby program and need a way to cut out an unneeded prefix
> substring and retain the substring that comes after it.
>
> Here are the actual details from my code:
>
> result.each do |item|
>  price = item.search(".price").text.match(/\d+[.]\d+/)
>  condition = item.search(".condition").text.match(/Used - ([^,]+)/)
>  rating = item.search(".rating a").text.to_i
>  seller = item.search(".seller b").text
>  puts "#{price} - #{condition} - #{rating} - #{seller}"
> end
>
> The one from condition [in the code above] is the one that is giving me
> a challenge. The string that is sent to condition will always be exactly
> one of the following and nothing else at all:
>
> "Used - Like New"
> "Used - Very Good"
> "Used - Good"
> "Used - Acceptable"
>
> I'm trying to get them to display as the following in the puts at the
> end of my code:
>
> "Like New"
> "Very Good"
> "Good"
> "Acceptable"
>
> The regex that I've got there in the condition line works in Rubular,
> but not in my code. I'm running 1.8.7 if that matters...

I am not sure which regexp you are referring to specifically.
However, you can do this

irb(main):001:0> s = "Used - Like New"
=> "Used - Like New"
irb(main):002:0> s[/\AUsed\s+-\s+(.*)\z/, 1]
=> "Like New"
irb(main):003:0> s[7..-1]
=> "Like New"

String#[] with regular expression is a very powerful tool - especially
when used with grouping as in this case.

> One last thing that I don't understand too is that in Rubular my regex
> for price shows the match in the "Match result:" line, but the regex for
> condition shows the whole string as a match in the "Match result:" line
> but shows the correctlt matching substring in the "Match captures:"
> line.

I am having difficulties to follow you here since I don't know what
"item" is in your case.  It's probably easier if you provide a simple
test case that demonstrates your point.  Using IRB often also helps.

> I'm grateful for this great resource (the list/forum) and would be very
> happy to hear from anyone who can help me sort this out!

We'll try to help but please provide a bit more information.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/