Hacking the Groovy Safe Navigation Operator in Ruby

safe_navigation_operator.rb

class Object

  # Given a method name that ends with ¤ call the method name without ¤.
  # If the method (excluding ¤) is not found call BasicObject#method_missing,
  # unless self is nil, in which case nil is returned.
  #
  # If the original method is the single character "¤" and self is nil,
  # return the first argument. This is the "Elvis" operator.
  #
  # Examples:
  #
  # p %w[array of words].reverse[2].upcase¤.slice¤(0, 3)
  # => "ARR"
  #
  # p %w[array of words].reverse[99].upcase¤.slice¤(0, 3)
  # => nil
  #
  # p %w[array of words].reverse[99].upcase¤.slice¤(0, 3) .¤ :default
  # => :default
  #
  def method_missing(name, *args, &block)
    return super unless name[-1] == "¤"
    return args.first if name.size == 1 && self == nil  # "Elvis" operator

    method = name.to_s.chop.to_sym

    if self == nil && !respond_to?(method)
      nil
    elsif respond_to?(method)
      send(method, *args, &block)
    else
      super(method, *args, &block)
    end
  end
end