[Ruby - saveする前の値の加工｜teratail](https://teratail.com/questions/213240)

reassign_order_index.rb

# frozen_string_literal: true

def reassign_order_index(hash)
  keys = hash.keys
  values = hash.values

  reordered_values =
    values.map.with_index(1) { |x, i| x.update('order' => i) }

  keys.zip(reordered_values).to_h
end

# 処理前
params = {
  'utf8' => '✓',
  'authenticity_token' =>
  'F98xi8sKXsi7vZmlhtGZpTXpMU0DsDv4FexHYHzVRgXpbkoiJF5429GL1+IIPGZMIo',
  'hoge' =>
  { '0' => { 'title' => 'title1', 'order' => '1' },
    '1' => { 'name' => 'title2', 'order' => '1' } },
  'fuga' =>
  { '0' => { 'name' => 'name', 'order' => '1' },
    '1' => { 'name' => 'title2', 'order' => '1' } },
  'commit' => '登録'
}

hoge = reassign_order_index(params.dig('hoge'))
fuga = reassign_order_index(params.dig('fuga'))

params.update('hoge' => hoge)
params.update('fuga' => fuga)

# 処理後
pp params
# =>
# {"utf8"=>"✓",
#  "authenticity_token"=>
#   "F98xi8sKXsi7vZmlhtGZpTXpMU0DsDv4FexHYHzVRgXpbkoiJF5429GL1+IIPGZMIo",
#  "hoge"=>
#   {"0"=>{"title"=>"title1", "order"=>1}, "1"=>{"name"=>"title2", "order"=>2}},
#  "fuga"=>
#   {"0"=>{"name"=>"name", "order"=>1}, "1"=>{"name"=>"title2", "order"=>2}},
#  "commit"=>"登録"}