Ruby capitalize every word first letter

Question

I need to make the first character of every word uppercase, and make the rest lowercase...

manufacturer.MFA_BRAND.first.upcase

is only setting the first letter uppercase, but I need this:

ALFA ROMEO => Alfa Romeo
AUDI => Audi
BMW => Bmw
ONETWO THREE FOUR => Onetwo Three Four

boulder_ruby · Answer 1 · 2019-06-13T03:00:50.763

In Rails:

"kirk douglas".titleize => "Kirk Douglas"
#this also works for 'kirk_douglas'

w/o Rails:

"kirk douglas".split(/ |\_/).map(&:capitalize).join(" ")

#OBJECT IT OUT
def titleize(str)
  str.split(/ |\_/).map(&:capitalize).join(" ")
end

#OR MONKEY PATCH IT
class String  
  def titleize
    self.split(/ |\_/).map(&:capitalize).join(" ")
  end
end

w/o Rails (load rails's ActiveSupport to patch #titleize method to String)

require 'active_support/core_ext'
"kirk douglas".titleize #=> "Kirk Douglas"

(some) string use cases handled by #titleize

"kirk douglas"
"kirk_douglas"
"kirk-douglas"
"kirkDouglas"
"KirkDouglas"

#titleize gotchas

Rails's titleize will convert things like dashes and underscores into spaces and can produce other unexpected results, especially with case-sensitive situations as pointed out by @JamesMcMahon:

"hEy lOok".titleize #=> "H Ey Lo Ok"

because it is meant to handle camel-cased code like:

"kirkDouglas".titleize #=> "Kirk Douglas"

To deal with this edge case you could clean your string with #downcase first before running #titleize. Of course if you do that you will wipe out any camelCased word separations:

"kirkDouglas".downcase.titleize #=> "Kirkdouglas"

There is also a gem [titleize](https://github.com/granth/titleize) that works nicely. — zhon, Oct 01 '13 at 16:06
Titleize isn't as simple as it looks, for instance 'hEy LoOK' becomes 'H Ey Lo Ok' — James McMahon, Jan 24 '14 at 21:47
HUGE GOTCHA, titleize will remove certain characters completely, such as the dash ( - ). "who? - me".titleize => "Who? Me" — pixelearth, Jun 18 '14 at 03:26
@pixelearth for me its converting all the dashes to individual spaces. — boulder_ruby, Feb 06 '15 at 02:52

score 230 · Accepted Answer · 2013-07-31T12:02:14.553

230

try this:

puts 'one TWO three foUR'.split.map(&:capitalize).join(' ')

#=> One Two Three Four

or

puts 'one TWO three foUR'.split.map(&:capitalize)*' '

edited Jul 31 '13 at 12:02

answered Nov 22 '12 at 21:29

9

`split` will split on space by default, so you can make it even shorter: `'one TWO three foUR'.split.map(&:capitalize).join(' ')` – Mischa Jun 13 '13 at 06:53
1

@waltee Could you possibly explain the `.map(&:capitalize)` or at least point to where in the doc you found it? I can't find any reference to that. Also, what is the deal with the `*' '` at the end of the second code snippet? – macsplean Oct 21 '13 at 07:02
7

@macsplean the `&:method` syntax in `map` is a [concise way to call a method on each item in the array](http://stackoverflow.com/questions/1217088/what-does-ampersand-colon-pretzel-colon-mean-in-ruby). You can then call `join` to turn that array into a string. The `* ' '` is an [alternative way to call join](http://brettu.com/ruby-ruby-tips-236-alternative-arrayjoin-syntax/). You can think of it as multiplying the items in the array together to create a string. – Andrew Nov 15 '13 at 21:13

score 38 · Answer 3 · edited May 11 '15 at 06:37

38

"hello world".titleize which should output "Hello World".

edited May 11 '15 at 06:37

Andrei Stefan

51,654
6
98
89

answered May 11 '15 at 06:15

tint lwin lwin win

405
4
4

This outputs `"One Two Three Fo Ur"` which is different than the desired output in this case, but may be desired in others. – Rick Smith Oct 06 '15 at 18:15
3

This isn't a Ruby method; it's an ActiveSupport (Rails) method introduced in v2.2.1 – Zack Burt Dec 29 '17 at 00:20

score 24 · Answer 4 · answered Dec 16 '13 at 12:40

24

Another option is to use a regex and gsub, which takes a block:

'one TWO three foUR'.gsub(/\w+/, &:capitalize)

answered Dec 16 '13 at 12:40

Bob Nadler

1,247
14
18

2

This one preserves inter-word dashes etc. – Beer Me Mar 28 '17 at 14:54
7

`.gsub(/\b\w/, &:capitalize)` preserves intended capitalization within words, e.g. "Jane mcCollins" – user3680688 Apr 04 '17 at 18:54
1

Using `[[:alpha:]]` instead of `\w` makes it unicode aware. – Adobe Apr 20 '21 at 10:30

score 5 · Answer 5 · edited Nov 23 '12 at 03:45

5

"hello world".split.each{|i| i.capitalize!}.join(' ')

edited Nov 23 '12 at 03:45

Himanshu

31,810
31
111
133

answered Nov 23 '12 at 03:21

Muhamamd Awais

2,385
14
25

1

there's no reason to use a bang (!) operator if you're not working with a variable – boulder_ruby Jul 19 '13 at 15:06
2

@boulder_ruby It's not true that *"there's no reason to use a bang operator if you're not working with a variable."* The return value of each iteration of the `each` block is being discarded. The `!` is modifying the strings produced by `split` in-place. Without the `!`, `capitalize` would be creating one new capitalized string per iteration, and then immediately discarding it. The final result would be `"hello world"`, just the same as the original string. With the `!`, each string in the `split`'d array is being changed, and therefore the result of `each` is an array of capitalized strings. – user513951 Feb 25 '14 at 00:06
1

Yeah you're just supposed to use `map`. Interesting hack though. Points – boulder_ruby Feb 25 '14 at 00:20

score 4 · Answer 6 · answered Nov 22 '12 at 21:25

4

Look into the String#capitalize method.

http://www.ruby-doc.org/core-1.9.3/String.html#method-i-capitalize

answered Nov 22 '12 at 21:25

Robert 'Jet' Rowe

687
6
15

1

String#capitalize downcases the rest of the string after the first letter. For names like "McGee", that is an undesired result, but it is partly useful in this case. – Br.Bill Apr 04 '18 at 02:00

score 1 · Answer 7 · answered Nov 19 '17 at 10:57

1

If you are trying to capitalize the first letter of each word in an array you can simply put this:

array_name.map(&:capitalize)

answered Nov 19 '17 at 10:57

astee

13
4

score 1 · Answer 8 · answered Jul 08 '20 at 22:43

I used this for a similar problem:

'catherine mc-nulty joséphina'.capitalize.gsub(/(\s+\w)/) { |stuff| stuff.upcase }

This handles the following weird cases I saw trying the previous answers:

non-word characters like -
accented characters common in names like é
capital characters in the middle of the string

Ruby capitalize every word first letter

8 Answers8

(some) string use cases handled by #titleize

#titleize gotchas

Linked

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