ruby-on-rails - 如果没有值，Rails 默认最大函数为零

Question

= trips.maximum(:maximum_speed_mph).round(0).to_s如果没有值，我如何将默认值设为零？

我能够做到这一点= number_with_precision(trips.average(:average_speed_mpg), :precision=>0) || 0

同样不适用于= trips.maximum(:maximum_speed_mph).round(0).to_s

score 3 · Accepted Answer

3

(trips.maximum(:maximum_speed_mph) || 0).round(0).to_s

于 2013-06-26T20:25:32.073 回答

score 3 · Accepted Answer

因为nil.to_i == 0你可以这样做：

max = trips.maximum(:maximum_speed_mph).to_i

然后将其转换为字符串max.to_s

如果您想为下一条记录自动分配值，这很有趣。例如

self.maximum_speed_mph = Trip.maximum_speed_mph.to_i + 1

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