hash.rb

class Hash
  def to_proc
    method(:[]).to_proc
  end

  def dig(*keys)
    result = fetch(keys.shift, nil)

    if result.is_a?(Hash) && keys.any?
      result.dig *keys
    else
      result
    end
  end
end

hash = {a: {b: {c: {d: {one: 1, two: 2, three: 3}}}}}

> %i[one three].map &hash.dig(*%i[a b c d])
=> [
    [0] 1,
    [1] 3
]

> %i[these keys do not exist].map &hash.dig(*%i[a b c d])
=> [
    [0] nil,
    [1] nil,
    [2] nil,
    [3] nil,
    [4] nil
]

> %i[one three].map &hash.dig(*%i[this branch does not exist])
=> [
    [0] nil,
    [1] nil
]