check_in.rb

    def add_missing_answers
      answer_count = @check_in.check_in_answers.length
      return if answer_count >= 4

      answers_to_add = 4 - answer_count
      answers_to_add.times do
        @check_in.check_in_answers.build
      end
    end

    def render obj
      return super if params[:action] == 'destroy'

      @check_in ||= check_in_by_id || new_check_in
      @check_in.valid? if validate_check_in?
      add_missing_answers

      super
    end

    def validate_check_in?
      params[:check_in] || !@check_in.new_record?
    end

    def check_in_by_id
      CheckIn.find(params[:id]) if params[:id].present?
    end

    def new_check_in
      CheckIn.new(params[:check_in])
    end