Find key/value pairs deep inside a hash containing an arbitrary number of nested hashes and arrays

Question

A web service is returning a hash that contains an unknown number of nested hashes, some of which contain an array, which in turn contains an unknown number of nested hashes

Answer 1

Ruby 2.3 introduces Hash#dig, which allows you to do:

h = { foo: {bar: {baz: 1}}}

h.dig(:foo, :bar, :baz)           #=> 1
h.dig(:foo, :zot)                 #=> nil

Answer 2

Combining a few of the answers and comments above:

class Hash
  def deep_find(key, object=self, found=nil)
    if object.respond_to?(:key?) && object.key?(key)
      return object[key]
    elsif object.is_a? Enumerable
      object.find { |*a| found = deep_find(key, a.last) }
      return found
    end
  end
end

Answer 3

Despite this appearing to be a common problem, I've just spent a while trying to find/come up with exactly what I need, which I think is the same as your requirement. Neither of the links in the first response are spot-on.

class Hash
  def deep_find(key)
    key?(key) ? self[key] : self.values.inject(nil) {|memo, v| memo ||= v.deep_find(key) if v.respond_to?(:deep_find) }
  end
end

So given:

hash = {:get_transaction_list_response => { :get_transaction_list_return => { :transaction => [ { ... 

The following:

hash.deep_find(:transaction)

will find the array associated with the :transaction key.

This is not optimal as the inject will continue to iterate even if memo is populated.