How to capitalize the first letter in a String in Ruby

Question

It depends on which Ruby version you use:

Ruby 2.4 and higher:

It just works, as since Ruby v2.4.0 supports Unicode case mapping:

"мария".capitalize #=> Мария

Ruby 2.3 and lower:

"maria".capitalize #=> "Maria"
"мария".capitalize #=> мария

The problem is, it just doesn’t do what you want it to, it outputs мария instead of Мария.

If you’re using Rails there’s an easy workaround:

"мария".mb_chars.capitalize.to_s # requires ActiveSupport::Multibyte

Otherwise, you’ll have to install the unicode gem and use it like this:

require 'unicode'

Unicode::capitalize("мария") #=> Мария

Ruby 1.8:

Be sure to use the coding magic comment:

#!/usr/bin/env ruby

puts "мария".capitalize

gives invalid multibyte char (US-ASCII), while:

#!/usr/bin/env ruby
#coding: utf-8

puts "мария".capitalize

works without errors, but also see the “Ruby 2.3 and lower” section for real capitalization.