ruby-on-rails - 如何优雅地处理 NilClass

Question

我试图避免由于 NilClass 而导致的 NoMethod 错误。我的代码如下所示:

@branded, @nonbranded, @unknown, @affiliate, @social, @referral, @paid, @direct, @email = [], [], [], [], [], [], [], [], []

count = 0
while count < 6
    date = SDLW + count
    #TODO There has to be a better way than this.
    branded_check = Metric.first(start_date: date, end_date: date, source: 'branded')
    nonbranded_check = Metric.first(start_date: date, end_date: date, source: 'nonbranded')
    unknown_check = Metric.first(start_date: date, end_date: date, source: 'unknown')
    affiliate_check = Metric.first(start_date: date, end_date: date, source: 'affiliate')
    social_check = Metric.first(start_date: date, end_date: date, source: 'social')
    referral_check = Metric.first(start_date: date, end_date: date, source: 'referral')
    paid_check = Metric.first(start_date: date, end_date: date, source: 'paid')
    direct_check = Metric.first(start_date: date, end_date: date, source: 'direct')
    email_check = Metric.first(start_date: date, end_date: date, source: 'email')

    branded_check = branded_check.nil? ? 0 : branded_check.visits
    nonbranded_check = nonbranded_check.nil? ? 0 : nonbranded_check.visits
    unknown_check = unknown_check.nil? ? 0 : unknown_check.visits
    affiliate_check = affiliate_check.nil? ? 0 : affiliate_check.visits
    social_check = social_check.nil? ? 0 : social_check.visits
    referral_check = referral_check.nil? ? 0 : referral_check.visits
    paid_check = paid_check.nil? ? 0 : paid_check.visits
    direct_check = direct_check.nil? ? 0 : direct_check.visits
    email_check = email_check.nil? ? 0 : email_check.visits

    @branded        << branded_check
    @nonbranded << nonbranded_check
    @unknown        << unknown_check
    @affiliate  << affiliate_check
    @social         << social_check
    @referral   << referral_check
    @paid           << paid_check
    @direct         << direct_check
    @email          << email_check

    count += 1
end

我确信必须有一种更简洁、更简洁的方法来做到这一点。尽管在谷歌上搜索和阅读，我还是没能弄明白。任何关于如何重构的想法都将不胜感激。

Answer 1

当然，创建一个避免重复自己的方法

def visits(tag, date)
  check = Metric.first(start_date: date, end_date: date, source: tag)    
  check.present? ? check.visits : 0   # or 'check.nil? ? 0 : check.visits' if you prefer
end

在你的方法中

count = 0
while count < 6
  date = SDLW + count

  @branded << visits('branded', date)
  @nonbranded << visits('nonbranded', date)
  ...

  count += 1
end