Simple regex problem in Rails

Question

Ok. It's late and I'm tired.

I want to match a character in a string. Specifically, the appearance of 'a'. As in "one and a half".

If I have a string which is all lowercase.

"one and a half is always good" # what a dumb example. No idea how I thought of that.

and I call titleize on it

"one and a half is always good".titleize #=> "One And A Half Is Always Good"

This is wrong because the 'And' and the 'A' should be lowercase. Obviously.

So, I can do

"One and a Half Is always Good".titleize.tr('And', 'and') #=> "One and a Half Is always Good"

My question: how do I make the "A" an "a" and without making the "Always" into "always"?

\ba\b The \b matches a word boundary. You are looking for the regex for that, right? — Stefan H
– Stefan H, Commented Dec 18, 2010 at 7:10
"One and A Half Is Always Good".gsub(/\bA\b/, 'a') # => "One and a Half Is Always Good" — Casual Coder
– Casual Coder, Commented Dec 18, 2010 at 8:11

the Tin Man · Accepted Answer · 2010-12-18 11:03:59Z

2

This does it:

require 'active_support/all'
str = "one and a half is always good" #=> "one and a half is always good"

str.titleize.gsub(%r{\b(A|And|Is)\b}i){ |w| w.downcase } #=> "One and a Half is Always Good"

or

str.titleize.gsub(%r{\b(A(nd)?|Is)\b}i){ |w| w.downcase } #=> "One and a Half is Always Good"

Take your pick of either of the last two lines. The regex pattern could be created elsewhere and passed in as a variable, for maintenance or code cleanliness.

edited Dec 18, 2010 at 11:03

answered Dec 18, 2010 at 8:16

the Tin Man

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Dogweather · Accepted Answer · 2010-12-18 12:44:36Z

2

I like Greg's two-liner (first titleize, then use a regex to downcase selected words.) FWIW, here's a function I use in my projects. Well tested, although much more verbose. You'll note that I'm overriding titleize in ActiveSupport:

class String
  #
  # A better titleize that creates a usable
  # title according to English grammar rules.
  #
  def titleize
    count  = 0
    result = []

    for w in self.downcase.split
      count += 1
      if count == 1
        # Always capitalize the first word.
        result << w.capitalize
      else
        unless ['a','an','and','by','for','in','is','of','not','on','or','over','the','to','under'].include? w
          result << w.capitalize
        else
          result << w
        end
      end
    end

    return result.join(' ')
  end
end

edited Dec 18, 2010 at 12:44

answered Dec 18, 2010 at 10:35

Dogweather

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3 Comments

the Tin Man Over a year ago

String has a titleize? You mean you're overriding Active_Support's titleize.

Phrogz Over a year ago

FWIW, it might be a good idea to convert your array of strings to a Hash for lookup. Calling Array#include? once for each word in each string to be titleized seems inefficient. stopwords = Hash[ %w[ a an and by for ... ].map{ |w| [w,true] }.flatten ] ... unless stopwords[w] ...

NJ. Over a year ago

Thanks for the help. this is a good solution but, you're right, Greg's is a little easier. Thanks!

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