How to compare strings ignoring the case

In case you have to compare UTF-8 strings ignoring case:

>> str1 = "Мария"
=> "Мария"
>> str2 = "мария"
=> "мария"
>> str1.casecmp(str2) == 0
=> false
>> require 'active_support/all'
=> true
>> str1.mb_chars.downcase.to_s.casecmp(str2.mb_chars.downcase.to_s) == 0
=> true

It works this way in Ruby 2.3.1 and earlier versions.

For smaller memory footprint you can cherry pick string/multibyte:

require 'active_support'
require 'active_support/core_ext/string/multibyte'

Edit, Ruby 2.4.0:

>> str1.casecmp(str2) == 0
=> false

So casecmp doesn't work in 2.4.0; However in 2.4.0 one can compare UTF-8 strings manually without active_support gem:

>> str1.downcase == str2.downcase
=> true

In Ruby 2.4.0 you have: casecmp?(other_str) → true, false, or nil

"abcdef".casecmp?("abcde")     #=> false
"aBcDeF".casecmp?("abcdef")    #=> true
"abcdef".casecmp?("abcdefg")   #=> false
"abcdef".casecmp?("ABCDEF")    #=> true

Here you have more info

You're looking for casecmp. It returns 0 if two strings are equal, case-insensitively.

str1.casecmp(str2) == 0

"Apple".casecmp("APPLE") == 0
#=> true

Alternatively, you can convert both strings to lower case (str.downcase) and compare for equality.