猫鼬在数组中查找元素 [英] Mongoose find element in array

问题描述

我刚开始使用猫鼬，遇到了寻找元素的问题...

I just started with Mongoose and having issues finding elements...

我的模式包含一个subregions数组，我想通过其code从中找到匹配的数组.该架构如下:

My schema contains an array of subregions from which I want to find the matching one by its code. The schema is the following:

 var schema = {
        name: {
            type: String,
            required: true
        }

        ...

        subRegions: [{
            name: {
                type: String,
                required: true
            },
            code: {
                type: String,
                required: true
            }
        }]

        ...

    };

我想出了

find({
    subRegions: {
        "$in": [{
            code: regionCode
        }]
    }
}).exec(...)

但这不起作用...

推荐答案

您的术语不正确，因为该结构不是多维"数组，因为这些结构具有数组中的数组"，因此具有维度".这只是数组中的对象".

Your terminology is off as that structure is not a "multi-dimensional" array, since those have "arrays within arrays", hence "dimensions". This is just "objects" within an array.

因此，您的问题是一个基本情况，即错误地处理了参数.您不需要 $in 来搜索数组，而是需要将参数的列表/数组"应用于该字段.

So your problem here is a basic case of having the arguments the wrong way around. You don't need $in just to search an array, but rather it takes a "list/array" of arguments to apply to the field.

简而言之，只需查找字段，然后使用点符号" :

In short, just lookup the field, and use "dot notation":

.find({ "subRegions.code": regionCode }).exec(...);

您基本上只需要$in来满足$or条件，便可以查找subRegions.code的替代值，因此当只有一个值要匹配时就不需要它.

You would only need $in for essentially an $or condition, looking up alternate values for subRegions.code, so you don't need that when there is only one value to match.

这篇关于猫鼬在数组中查找元素的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！