alternating_case_<=>_alternating_case.md

altERnaTIng cAsE <=> ALTerNAtiNG CaSe

Description

altERnaTIng cAsE <=> ALTerNAtiNG CaSe

Define String.prototype.toAlternatingCase (or a similar function/method such as to_alternating_case/toAlternatingCase/ToAlternatingCase in your selected language; see the initial solution for details) such that each lowercase letter becomes uppercase and each uppercase letter becomes lowercase. For example:

"hello world".to_alternating_case() === "HELLO WORLD"
"HELLO WORLD".to_alternating_case() === "hello world"
"hello WORLD".to_alternating_case() === "HELLO world"
"HeLLo WoRLD".to_alternating_case() === "hEllO wOrld"
"12345".to_alternating_case()       === "12345"                 # Non-alphabetical characters are unaffected
"1a2b3c4d5e".to_alternating_case()  === "1A2B3C4D5E"
"String.prototype.toAlternatingCase".to_alternating_case() === "sTRING.PROTOTYPE.TOaLTERNATINGcASE"

As usual, your function/method should be pure, i.e. it should not mutate the original string.

My Solution

class String
  def to_alternating_case
    self.chars.map { |el| el == el.downcase ? el.upcase : el.downcase}.join
  end
end

Better/Alternative solution from Codewars

class String
  def to_alternating_case
    self.swapcase
  end
end