ruby-on-rails - 如果条件为真，我该如何分配条件（查询），或者如果条件为假，如何进行另一项分配？

Question

我怎样才能避免打字

TypeOfVoyagePortActivity.find_by_description(activity_description)

两次？

这是我在其中使用它的上下文：

 if TypeOfVoyagePortActivity.find_by_description(activity_description)
   pl.activity = TypeOfVoyagePortActivity.find_by_description(activity_description)
 else
   pl.activity = TypeOfVoyagePortActivity.find_by_description("Custom") 
 end

Answer 1

model = TypeOfVoyagePortActivity
pl.activity = model.find_by_description(activity_description) ||
  model.find_by_description("Custom")

Answer 2

您可以将结果分配给find_by_description变量

 if t = TypeOfVoyagePortActivity.find_by_description(activity_description)
   pl.activity = t
 else
   pl.activity = TypeOfVoyagePortActivity.find_by_description("Custom") 
 end

或者作为更好的选择：

p1.activity = [activity_description, "Custom"].each_with_object(nil) do |a, memo|
  memo ||= TypeOfVoyagePortActivity.find_by_description(a)
end