过滤ActiveRecord关系...如果没有匹配项。 （空活动记录关系）

Question

我有一个仪表板，允许通过不同的参数过滤结果。我构建了按给定标准过滤结果的方法。我遇到问题的一个方面是前一行是否应该使活动记录关系无效。我应该把一堆如果存在吗？ STAT

def find_website_stats(options = {})
    if options[:date_between].present?
      start_date = options[:date_between].split(/-/).first.to_date
      end_date = options[:date_between].split(/-/).last.to_date + 1
    elsif options[:start_date].present?
      start_date = options[:start_date].to_date
      end_date = options[:end_date].to_date + 1 if options[:end_date].present?
    end

    contractor_name = options[:search_contractor] if options[:search_contractor].present?
    distributor_name = options[:search_distributor] if options[:search_distributor].present?
    distributor_ids = options[:with_distributor] if options[:with_distributor].present?
    contractor_ids = options[:with_contractor] if options[:with_contractor].present?
    with_country = options[:with_country] if options[:with_country].present?
    with_state = options[:with_state] if options[:with_state].present?
    search_city = options[:search_city] if options[:search_city].present?

    web_stats = self.website_stats

    if web_stats.present?
      web_stats = web_stats.where(contractor_id: [*contractor_ids]) if contractor_ids.present?
      if distributor_ids.present?
        web_stat_ids = DistributorWebsiteStat.where(distributor_id: [*distributor_ids]).pluck(:website_stat_id)
        web_stats = web_stats.where(id: [*web_stat_ids])
      end
      web_stats = web_stats.where(date_recorded: start_date..end_date) if start_date.present? && end_date.present?
      web_stats = web_stats.with_country(with_country) if with_country.present?
      web_stats = web_stats.with_state(with_state) if with_state.present?
      web_stats = web_stats.search_city(search_city) if search_city.present?

      #untested
      if contractor_name.present?
        searched_contractor_ids = Brand.search_contractor(contractor_name).pluck(:id)
        web_stats = web_stats.where(contractor_id: [*searched_contractor_ids])
      end

      if distributor_name.present?
        searched_distributor_ids = Brand.search_distributor(distributor_name).pluck(:id)
        web_stat_ids = DistributorWebsiteStat.where(distributor_id: [*searched_distributor_ids])
        web_stats = web_stats.where(id: [*web_stat_ids])
      end
      #end untested
    end

    web_stats
end

我现在特别遇到问题的是说明是否有web_stat_ids.present？

首先，我抓住了这个对象所关联的所有网站统计数据，然后查看给定的经销商是否有任何数据。

如果给定的经销商没有，web_stat_ids显然会返回nil

然后当我去web_stats.where（id：[* web_stat_ids]）时，显然会返回我以前的相同的东西，而不是一个空的活动记录关系，这就是我需要它？

如果我将它设为空数组，那么带有“where”的下几个语句将不起作用，因为它是一个数组而不是一个活动的记录关系。

我知道我可以将这些东西包装成一堆如果存在的话？ ＆安培;＆安培;陈述......但我想知道我的问题是否有更好的解决方案？

Answer 1

如果有其他人正在寻找此项，请从此SO帖子中找到答案：How to return an empty ActiveRecord relation?

Model.none rails 4 +