[Ruby] Convert from snake_case to camel_case

snake_to_camel.rb

# Using gsub (least performant)

"test_string".capitalize.gsub(/_(\w)/){$1.upcase} # => TestString

# Using split & map with capitalize

"test_string".split('_').map(&:capitalize).join

# Using split & map (most performant)

"test_string".split('_').map{|e| e.capitalize}.join

# Ruby string implementation
http://rubydoc.info/gems/extlib/0.9.15/String#camel_case-instance_method

def camel_case
  return self if self !~ /_/ && self =~ /[A-Z]+.*/
  split('_').map{|e| e.capitalize}.join
end

# Extra

"hello_world".split('_').collect(&:capitalize).join #=> "HelloWorld"