Feature flag

Change Ruby code during runtime

class Document
  attr_accessor :text

  def self.toggle_encryption(state: true)
    if state
      def encrypt
        StrongEncryptor.call text
      end
    else
      def encrypt
        Encryptor.call text
      end
    end
  end
  toggle_encryption
end

Calling Document.toggle_encryption(state: true) will change the instance method encrypt to use StrongEncryptor implementation. Similarly, calling it with state: false will change the implementation to use Encryptor. This is a naive, contrived example that will not work for multi-process production environments, but it is still useful for hacking and debugging.