【Rails 6】form_with用いて一括登録する

# Memoテーブル
# id : integer
# title : string

class Memo < ApplicationRecord
  validates :title, presence: true
end

class MemosController < ApplicationController
  def index
    @memos = Memo.all
  end

  def new
    @form = Form::MemoCollection.new
  end

  def create
    @form = Form::MemoCollection.new(memo_collection_params)
    if @form.save
      redirect_to new_memo_path
    else
      render :new
    end
  end

  private
    def memo_collection_params
      params
        .require(:form_memo_collection)
        .permit(memos_attributes: :title)
    end
end

= form_with( model: @form ,url: memos_path, method: :post) do |f|
  = f.fields_for :memos do |i|
    = i.text_field :title
    
  = f.submit "送信"

class Memo < ApplicationRecord
  validates :title, presence: true
end

class Form::MemoCollection < Form::Base
  FORM_COUNT = 3
  attr_accessor :memos

  def initialize(attributes = {})
    super attributes
    self.memos = FORM_COUNT.times.map { Memo.new() } unless self.memos.present?
  end
  
  # 上でsuper attributesとしているので必要
  def memos_attributes=(attributes)
    self.memos = attributes.map { |_, v| Memo.new(v) }
  end

  def save
    # 実際にやりたいことはこれだけ
    # self.memos.map(&:save!)

    # 複数件全て保存できた場合のみ実行したいので、transactionを使用する
    Memo.transaction do
      self.memos.map(&:save!)
    end
      return true
    rescue => e
      return false
  end
end

class Form::Base
  include ActiveModel::Model
  include ActiveModel::Callbacks
  include ActiveModel::Validations
  include ActiveModel::Validations::Callbacks
end