Converting upper-case string into title-case using Ruby

Question

I\'m trying to convert an all-uppercase string in Ruby into a lower case one, but with each word\'s first character being upper case. Example:

convert \"MY STRING HE

Answer 1

If you're using Rails (really all you need is ActiveSupport, which is part of Rails), you can use titleize:

"MY STRING HERE".titleize
# => "My String Here"

Answer 2

The ruby core itself has no support to convert a string from upper (word) case to capitalized word case.

So you need either to make your own implementation or use an existing gem.

There is a small ruby gem called lucky_case which allows you to convert a string from any of the 10+ supported cases to another case easily:

require 'lucky_case'

# to get capital word case as string
LuckyCase.capital_word_case('MY STRING HERE')    # => 'My String Here'
# or the opposite way
LuckyCase.upper_word_case('Capital Word Case')   # => 'MY STRING HERE'

You can even monkey patch the String class if you want to:

require 'lucky_case/string'

'MY STRING HERE'.capital_word_case  # => 'My String Here'
'MY STRING HERE'.capital_word_case! # => 'My String Here' and overwriting original

Have a look at the offical repository for more examples and documentation:

https://github.com/magynhard/lucky_case

Answer 3

"HELLO WORLD HOW ARE YOU".gsub(/\w+/) do |word|
  word.capitalize
end
#=> "Hello World How Are You"

Answer 4

I've try to improve code... ready for critics and suggestions.

class Book
    attr_accessor :title
    def title=(new_title)
    notcap=%w(and the a in of an)
    str=''
    new_title.gsub(/(\w|\s)\w+/) do |word|
        word.strip!
        if not notcap.include? word
               word.capitalize! 
        end
       str += ' ' + word 
    end
    str.strip!
    str = str[0].upcase + str[1..-1]
    @title = str
   end
end

Answer 5

From ActiveSupport

"MY STRING HERE".gsub(/\b('?[a-z])/) { $1.capitalize }

If you are using Rails/ActiveSupport, the method is already available for free.

Answer 6

While trying to come up with my own method (included below for reference), I realized that there's some pretty nasty corner cases. Better just use the method already provided in Facets, the mostest awesomest Ruby library evar:

require 'facets/string/titlecase'

class String
  def titleize
    split(/(\W)/).map(&:capitalize).join
  end
end

require 'test/unit'
class TestStringTitlecaseAndTitleize < Test::Unit::TestCase
  def setup
    @str = "i just saw \"twilight: new moon\", and man!   it's crap."
    @res = "I Just Saw \"Twilight: New Moon\", And Man!   It's Crap."
  end
  def test_that_facets_string_titlecase_works
    assert_equal @res, @str.titlecase
  end
  def test_that_my_own_broken_string_titleize_works
    assert_equal @res, @str.titleize # FAIL
  end
end

If you want something that more closely complies to typical writing style guidelines (i.e. does not capitalize words like "and"), there are a couple of "titleize" gems on GitHub.