Ruby Hash#fetch_path

hash_ext.rb

class Hash
  def fetch_path(path, default = nil)
    pieces = path.split('.', 2)
    value = self[pieces[0]]
    return value if value && !pieces[1]
    return default if !value.respond_to?(:fetch_path) || !value

    value.fetch_path(pieces[1], default)
  end
end

hash_ext_spec.rb

require 'spec_helper'

describe Hash do
  describe "#fetch_path" do
    let(:a_hash) {
      { 'foo' => { 'bar' => { 'baz' => 'quux' }, 'ip' => 17 }}
    }
    it "allows you to safely reach into a hash through many levels" do
      a_hash.fetch_path('foo.bar.baz').should == 'quux'
    end
    it "works in a trivial case (but just use #fetch plz!)" do
      a_hash.fetch_path('foo').should == { 'bar' => { 'baz' => 'quux' }, 'ip' => 17 }
    end
    it "returns nil if you don't supply a default and the keypath doesn't exist" do
      a_hash.fetch_path('foo.b').should be_nil
    end
    it "returns the default if it cannot follow the path through and one is supplied" do
      a_hash.fetch_path('foo.b', 'a_default').should == 'a_default'
    end
    it "returns the default if the path terminates in a non-hash early" do
      a_hash.fetch_path('foo.ip.ping', 'pong').should == 'pong'
    end
  end
end