How to convert a string to lower or upper case in Ruby

Question

How do I take a string and convert it to lower or upper case in Ruby?

Answer 1

Like @endeR mentioned, if internationalization is a concern, the unicode_utils gem is more than adequate.

$ gem install unicode_utils
$ irb
> require 'unicode_utils'
=> true
> UnicodeUtils.downcase("FEN BİLİMLERİ", :tr)
=> "fen bilimleri"

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String manipulations in Ruby 2.4 are now unicode-sensitive.

Answer 2

In combination with try method, to support nil value:

'string'.try(:upcase)
'string'.try(:capitalize)
'string'.try(:titleize)

Answer 3

The .swapcase method transforms the uppercase latters in a string to lowercase and the lowercase letters to uppercase.

'TESTING'.swapcase #=> testing
'testing'.swapcase #=> TESTING

Answer 4

Won't work for every, but this just saved me a bunch of time. I just had the problem with a CSV returning "TRUE or "FALSE" so I just added VALUE.to_s.downcase == "true" which will return the boolean true if the value is "TRUE" and false if the value is "FALSE", but will still work for the boolean true and false.

Answer 5

You can find out all the methods available on a String by opening irb and running:

"MyString".methods.sort

And for a list of the methods available for strings in particular:

"MyString".own_methods.sort

I use this to find out new and interesting things about objects which I might not otherwise have known existed.

Answer 6

The ruby downcase method returns a string with its uppercase letters replaced by lowercase letters.

"string".downcase

https://ruby-doc.org/core-2.1.0/String.html#method-i-downcase