Recursive Hash

recursive_hash.rb

# lib file contents

Hash.class_eval do
  # how the hell do we get this to work with []

  def recursive_find(key)
    return self[key] if has_key?(key)

    self
      .values
      .select { |value| value.is_a?(Hash) }
      .find { |hash| hash.has_key?(key) ? hash[key] : hash.recursive_find(key) }
  end
end

# spec file contents

require 'spec_helper'
require './lib/recursive_hash'

describe "recursive hash" do
  let(:hash) do
    {
      a: 1,
      b: { c: 2 },
      d: { e: { f: 3, i: 5 }},
      g: { f: 4 }
    }
  end

  it "acts like a normal hash when key present in top level" do
    expect(hash.recursive_find(:a)).to be 1
  end

  it "can retrieve a value from a nested hash if key not present in top level" do
    expect(hash.recursive_find(:c)).to be 2
  end

  it "can retrieve a value from a deeply nested hash if key not in any higher leaf node" do
    expect(hash.recursive_find(:i)).to be 5
  end

  it "can retrieve a value with a duplicated key, which would be the least nested value" do
    expect(hash.recursive_find(:f)).to be 4
  end
end