Ruby on Rails:返回零的地方 [英] Ruby on Rails: where returning nil

问题描述

在我的应用中，我获得了某个类别，并且根据其名称过滤了相关项目. 下面的代码应该很清楚:

In my app I'm obtaining a certain category, and I'm filtering the associated items based on their name. The following code should be pretty clear:

categories = Category.where(:id => params[:category_id]).includes(:items).where("lower(items.name) like ?", "%#{params[:keywords].downcase}%")

但是，如果名称过滤器排除了所有项目，则where返回的categories对象为nil.这是预期的行为吗?即使项目不存在，如何获取类别?

However, if the name filter excludes all the items, the categories object returned by where is nil. Is this the expected behaviour? How can I get the category even either items exist or not?

推荐答案

最简单的方法可能就是拆分查询:

The easiest way might be to just split the query:

@category = Category.find(params[:category_id])
@items = @category.items.where("lower(items.name) like ?", "%#{params[:keywords].downcase}%")

根据您的代码，似乎category_id仅引用1个类别，因此我将其更改为单数.

Based on your code it seems like category_id references only 1 category so I've changed it to singular.

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