Converting upper-case string into title-case using Ruby

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 HERE" to "My String Here".

I know I can use the .downcase method, but that would make everything lower case ("my string here"). I'm scanning all lines in a file and doing this change, so is there a regular expression I can use through ruby to achieve this?

Thanks!

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"

If you're using plain Ruby but don't mind loading a small amount of ActiveSupport you can require it first:

require 'active_support/core_ext/string/inflections'
# => true
"MY STRING HERE".titleize
# => "My String Here"

N.B. By default titleize doesn't handle acronyms well and will split camelCaseStrings into separate words. This may or may not be desirable:

"Always use SSL on your iPhone".titleize
# => "Always Use Ssl On Your I Phone"

You can (partially) address this by adding "acronyms":

require 'active_support/core_ext/string/inflections' # If not using Rails
ActiveSupport::Inflector.inflections do |inflect|
  inflect.acronym 'SSL'
  inflect.acronym 'iPhone'
end
"Always use SSL on your iPhone".titleize
# => "Always Use SSL On Your IPhone"

For those who speak the Queen's English (or who struggle to spell titleize), there's no .titleise alias but you can use .titlecase instead.

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

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.

From ActiveSupport

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

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

string = "MY STRING HERE"
string.split(" ").map {|word| word.capitalize}.join(" ")

The way this works: The .split(" ") splits it on spaces, so now we have an array that looks like ["my", "string", "here"]. The map call iterates over each element of the array, assigning it to temporary variable word, which we then call capitalize on. Now we have an array that looks like ["My", "String", "Here"], and finally we turn that array back into a string by joining each element with a space (" ").

"MY STRING HERE".titlecase

Does the job (it's a method in the Rails gem, however) http://apidock.com/rails/String/titlecase

Unicode-aware titlecase for Ruby 2.4.0+:

class String
  def titlecase
    split(/([[:alpha:]]+)/).map(&:capitalize).join
  end
end

>> "я только что посмотрел \"леди исчезает\", и это чума!".titlecase
=> "Я Только Что Посмотрел \"Леди Исчезает\", И Это Чума!"

(based on https://stackoverflow.com/a/1792102/788700)

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

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

Capitalizes every word in a sentence using ruby, without regex.. because unfortunately those scare me

class Book
	attr_accessor :title
	def title=(new_title)
		result = []
		words = new_title.split(' ')
		words.each do |word|
			capitalized = word[0].upcase + word[1..word.length].downcase
			result.push(capitalized)
		end
		
		@title = result.join(' ')
	end
end