Hash#fetch_recursively for Ruby

examples.rb

# encoding: utf-8

# examples:
nested_hashes = {:a=>{:b=>{:c=>{:more=>"answer"}}}, :num=>42}
path = [:a, :b, :c, :more]
nested_hashes.fetch_recursively(path) #=> "answer"
nested_hashes.fetch_recursively([:num]) #=> 42
# wrong:
nested_hashes.fetch_recursively(:a) # raises NoMethodError; should pass an Array
nested_hashes.fetch_recursively([:num, :something]) # raises NoMethodError; can’t fetch from 42
nested_hashes.fetch_recursively([:a, :nosuch]) # raises KeyError; the hash in :a doesn’t have key :nosuch

implementation.rb

# encoding: utf-8

class Hash
	# fetches the first key from this hash, then the next key from that resulting hash, etc.
	# for navigating nested hashes in an alternative way – `hash.fetch_recursively [1, 2, 3]` instead of `hash[1][2][3]`.
	# raises a KeyError if any of the keys don’t exist in their hashes
	# raises a NoMethodError if any of the interstitial values don’t respond to :fetch
	def fetch_recursively(path)
		path.inject(self, :fetch)
		# “inject” rather than “reduce” because it’s really self that is being reduced down more than path. I am injecting the path into self to get a changed self.
	end
end