Example of implementing a simple #dig for #ruby IRC

dry_product.rb

# For "fun," a DRY metaprogrammed version
class Product
  ATTRIBUTES = %i[name price]

  ATTRIBUTES.each { |attribute| attr_reader attribute }

  def initialize(**keywords)
    missing = ATTRIBUTES - keywords.keys
    if missing.any?
      message = "missing keywords: #{missing}.map(&:inspect).join(', ')"
      raise ArgumentError, message
    end

    ATTRIBUTES.each do |attribute|
      keyword = keywords.fetch(attribute)
      instance_variable_set :"@#{attribute}", keyword
    end
  end

  def dig(key)
    instance_variable_get(:"@#{key}") if ATTRIBUTES.include?(key.to_sym)
  end
end

product = Product.new(name: 'scissors', price: 8)
array = [product]
array.dig(0, :name)
#=> "scissors"

product.rb

class Product
  attr_reader :name
  attr_reader :price

  def initialize(name:, price:)
    @name = name
    @price = price
  end

  def dig(key)
    case key.to_sym
    when :name
      @name
    when :price
      @price
    end
  end
end

product = Product.new(name: 'scissors', price: 8)
array = [product]
array.dig(0, :name)
#=> "scissors"