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 (" ").

Converting upper-case string into title-case using Ruby

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