snake_case, camelCase, and PascalCase extension methods for Ruby's String class.

case_conversion.rb

class String

  def snake_case
    gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2')
        .gsub(/([a-z\d])([A-Z])/,'\1_\2')
        .tr("-", "_")
        .downcase
  end

  def camel_case
    sub(/^(?:(?=\b|[A-Z_])|\w)/) { $&.downcase }
        .gsub(/(?:_|(\/))([a-z\d]*)/) { "#{$1}#{$2.capitalize}" }
  end

  def pascal_case
    sub(/^[a-z\d]*/) { $&.capitalize }
    .gsub(/(?:_|(\/))([a-z\d]*)/) { "#{$1}#{$2.capitalize}" }
  end
end