Ruby on Rails uncapitalize first letter

Question

I'm running Rails 2.3.2.

How do I convert "Cool" to "cool"? I know "Cool".downcase works, but is there a Ruby/Rails method that does the opposite of capitalize, i.e., uncapitalize or decapitalize?

score 120 · Answer 1 · edited Nov 28 '12 at 19:18

120

There is also:

"coolat_cat".camelize(:lower) # => "coolCat"

edited Nov 28 '12 at 19:18

gerry3

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answered Oct 26 '12 at 08:46

tfischbach

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This does require ActiveRecord tho : http://apidock.com/rails/String/camelize (After reading the question, it does state it is already with Rails) – Ian Vaughan May 28 '13 at 21:51
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@Ian Vaughan: ActiveSupport to be more precise – tfischbach May 29 '13 at 10:26
They updated the method signature around v4.2.7. It now takes a boolean, like `camelize(uppercase_first_letter = true)` http://apidock.com/rails/v4.2.7/String/camelize – animatedgif Nov 15 '16 at 03:39
1

@animatedgif there's two methods, [Inflector.#camelize(term, uppercase_first_letter)](http://www.rubydoc.info/gems/activesupport/4.2.7.1/ActiveSupport/Inflector#camelize-instance_method) which takes a string to camelize and a boolean, [String#camelize(first_letter)](http://www.rubydoc.info/gems/activesupport/4.2.7.1/String#camelize-instance_method) which camelizes `self` and takes a symbol `:upper` or `:lower`. I think the apidock docs are in error. – David Moles Dec 15 '16 at 18:40
Definitely a rails thing but damn its nice to have! – Dan Bradbury Mar 13 '17 at 20:25

Jacob Relkin · Accepted Answer · 2011-02-03T17:03:12.283

52

There is no inverse of capitalize, but you can feel free to roll your own:

class String
  def uncapitalize 
    self[0, 1].downcase + self[1..-1]
  end
end

edited Feb 03 '11 at 17:03

answered Dec 17 '10 at 19:31

Jacob Relkin

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Where should we add this method? – Vadorequest Jul 16 '14 at 09:02
@Vadorequest The method? Add it on the String class, as shown in the answer. – Ajedi32 Aug 08 '14 at 15:36
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In a standard Rails app, it would probably make sense to add it to a new file in `/config/initializers` – DaveMongoose Aug 08 '14 at 15:51
@Ajedi32 Well, it maybe looks obvious to you, but not to me. Thanks Dave. – Vadorequest Aug 09 '14 at 21:14

score 11 · Answer 3 · answered Feb 01 '13 at 15:52

11

You could also do this with a simple sub:

"Cool".sub(/^[A-Z]/) {|f| f.downcase }

answered Feb 01 '13 at 15:52

JP.

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5

note that `"Cool".sub(/^[A-Z]/, &:downcase)` is enough – astreal Jun 16 '15 at 13:42
1

`"CoolTrick".sub(/^[[:alpha:]]/) {|f| f.downcase }` – Eduardo Santana Feb 14 '17 at 01:51

score 9 · Answer 4 · answered Aug 08 '14 at 15:33

9

str = "Directly to the south"
str[0] = str[0].downcase
puts str
#=> "directly to the south"

answered Aug 08 '14 at 15:33

boulder_ruby

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This not only the most readable method, but also and by far the most performant one, even if you protect it by some kind of ternary operator or if statement to ensure that str is not nil. This should be the accepted answer. Thanks @boulder_ruby – Freddo Apr 10 '16 at 01:06

iain · Answer 5 · 2010-12-18T11:00:28.230

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There is no real inverse of capitalize, but I think underscore comes close.

"CoolCat".underscore  #=> "cool_cat"
"cool_cat".capitalize #=> "Cool_cat"
"cool_cat".camelize   #=> "CoolCat"

Edit: underscore is of course the inverse of camelize, not capitalize.

edited Dec 18 '10 at 11:00

answered Dec 17 '10 at 19:28

iain

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score 3 · Answer 6 · edited Dec 01 '17 at 03:01

3

You can use tap (so that it fits on one line):

"JonSkeet".tap { |e| e[0] = e[0].downcase } # => "jonSkeet"

edited Dec 01 '17 at 03:01

Jon Schneider

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answered Mar 21 '16 at 14:03

Benjamin Crouzier

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score 2 · Answer 7 · answered Oct 28 '16 at 14:46

2

There is an inverse of capitalize called swapcase:

"Cool Cat".swapcase   #=> "cOOL cAT"

answered Oct 28 '16 at 14:46

Nitin Savant

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score 2 · Answer 8 · answered May 24 '23 at 22:16

String#downcase_first (Rails 7.1+)

Starting from Rails 7.1, there is a String#downcase_first method:

Converts the first character to lowercase.

For example:

'If they enjoyed The Matrix'.downcase_first # => "if they enjoyed The Matrix"
'I'.downcase_first                          # => "i"
''.downcase_first                           # => ""

Sources:

score 1 · Answer 9 · edited Dec 24 '16 at 11:53

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name = "Viru"

name = name.slice(0).downcase + name[1..(name.length)]

edited Dec 24 '16 at 11:53

Danila Ganchar

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answered Dec 24 '16 at 11:46

Navnath

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score 1 · Answer 10 · answered May 30 '17 at 13:39

1

Try this

'Cool'.sub(/^([A-Z])/) { $1.tr!('[A-Z]', '[a-z]') }

https://apidock.com/ruby/XSD/CodeGen/GenSupport/uncapitalize

answered May 30 '17 at 13:39

Rahul Patel

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score 1 · Answer 11 · answered Dec 17 '10 at 19:31

1

If you use Ruby Facets, you can lowercase the first letter:

https://github.com/rubyworks/facets/blob/master/lib/core/facets/string/uppercase.rb

answered Dec 17 '10 at 19:31

rmk

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Ruby on Rails uncapitalize first letter

11 Answers11

String#downcase_first (Rails 7.1+)

Linked