Recursive closed struct.

recursive_closed_struct.rb

class RecursiveClosedStruct
  def initialize(hash)
    @hash = hash
  end

  def method_missing(name, *)
    value = fetch(name)
    if value.is_a?(Hash)
      self.class.new(value)
    else
      value
    end
  end

  private

  def fetch(name)
    @hash.fetch(name) do
      raise NoMethodError.new("undefined method `#{name}' for #{self}")
    end
  end
end

recursive_closed_struct_spec.rb

require "minitest/autorun"
require "minitest/pride"
require "recursive_closed_struct"

describe RecursiveClosedStruct do
  it "provides readers from a hash" do
    subject = RecursiveClosedStruct.new(key: "value")
    assert_equal "value", subject.key
  end

  it "raises when there's no such key" do
    subject = RecursiveClosedStruct.new(key: "value")
    assert_raises(NoMethodError) do
      subject.other_key
    end
  end

  it "recurses through hashes" do
    subject = RecursiveClosedStruct.new({
      one: { two: { three: "four" } }
    })
    assert_equal "four", subject.one.two.three
  end
end

Note: currently assumes hash has symbol keys.