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

Ruby has a few methods for changing the case of strings. To convert to lowercase, use downcase:

"hello James!".downcase    #=> "hello james!"

Similarly, upcase capitalizes every letter and capitalize capitalizes the first letter of the string but lowercases the rest:

"hello James!".upcase      #=> "HELLO JAMES!""hello James!".capitalize  #=> "Hello james!""hello James!".titleize    #=> "Hello James!" (Rails/ActiveSupport only)

If you want to modify a string in place, you can add an exclamation point to any of those methods:

string = "hello James!"string.downcase!string   #=> "hello james!"

Refer to the documentation for String for more information.

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.

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"

String manipulations in Ruby 2.4 are now unicode-sensitive.