Just like Hash#deep_merge but works with Arrays, applying the default to each element inside it.

hash_deeper_merge.rb

class Hash
  def deeper_merge(overriding_hash)
    ret = self.merge(overriding_hash) do |key, default_val, overriding_val|
      if default_val.class == Array and overriding_val.class == Array
        resulting_array = []
        for little_hash in overriding_val
          resulting_array << default_val.first.deeper_merge(little_hash)
        end
        resulting_array
      else
        default_val = default_val.to_hash if default_val.respond_to?(:to_hash)
        overriding_val = overriding_val.to_hash if overriding_val.respond_to?(:to_hash)
        default_val.class.to_s == 'Hash' && overriding_val.class.to_s == 'Hash' ? default_val.deeper_merge(overriding_val) : overriding_val
      end
    end
    return ret
  end
end

#> default = {a: 1, b:1, c: [{a:1, b:1}]}
#=> {:a=>1, :b=>1, :c=>[{:a=>1, :b=>1}]}
#
#> default.deeper_merge({b:5, c:[{b:5,c:1},{a:3,c:2},{a:3,b:4,c:2}]})
#=> {:a=>1,
# :b=>5,
# :c=>[{:a=>1, :b=>5, :c=>1}, {:a=>3, :b=>1, :c=>2}, {:a=>3, :b=>4, :c=>2}]}
#
#> default.deeper_merge({b:5, c:[{b:5,c:1},{a:3,c:2},{a:3,b:4,c:2},{}]})
#=> {:a=>1,
# :b=>5,
# :c=>
#  [{:a=>1, :b=>5, :c=>1},
#   {:a=>3, :b=>1, :c=>2},
#   {:a=>3, :b=>4, :c=>2},
#   {:a=>1, :b=>1}]