1 files changed, 29 insertions, 0 deletions
diff --git a/lib/hashie/extensions/deep_fetch.rb b/lib/hashie/extensions/deep_fetch.rb
new file mode 100644
index 0000000..d8746cb
--- /dev/null
+++ b/lib/hashie/extensions/deep_fetch.rb
@@ -0,0 +1,29 @@
+module Hashie
+  module Extensions
+    # Searches a deeply nested datastructure for a key path, and returns the associated value.
+    #
+    #  options = { user: { location: { address: '123 Street' } } }
+    #  options.deep_fetch :user, :location, :address #=> '123 Street'
+    #
+    # If a block is provided its value will be returned if the key does not exist.
+    #
+    #  options.deep_fetch(:user, :non_existent_key) { 'a value' } #=> 'a value'
+    #
+    # This is particularly useful for fetching values from deeply nested api responses or params hashes.
+    module DeepFetch
+      class UndefinedPathError < StandardError; end
+
+      def deep_fetch(*args, &block)
+        args.reduce(self) do |obj, arg|
+          begin
+            arg = Integer(arg) if obj.kind_of? Array
+            obj.fetch(arg)
+          rescue ArgumentError, IndexError => e
+            break block.call(arg) if block
+            raise UndefinedPathError, "Could not fetch path (#{args.join(' > ')}) at #{arg}", e.backtrace
+          end
+        end
+      end
+    end
+  end
+end