从Mongoose查询返回的查找没有匹配项？ [英] What is returned from Mongoose query that finds no matches?

问题描述

我有点困惑阅读Mongoose文档。

I'm a little confused reading the Mongoose documentation.

如果我在mongoose中运行一个没有匹配集合中的文档的查询，则 err 结果在回调函数 callback（err，results）？我只是不知道Mongoose认为一个错误。作为一个数学家，返回空集合（即 results 数组为空）似乎完全有效，不应该是一个错误 - 查询执行得很好，只有没有匹配文件。另一方面，有些人可能认为它是错误。从mongoose文档，可以：

If I run a query in mongoose which matches no documents in the collection, what are the values of err and results in the callback function callback(err, results)? I just don't know what Mongoose considers an "error". As a mathematician, returning the empty set (i.e. results array empty) seems perfectly valid and shouldn't be an "error" - the query executed fine, there was just no matching documents. On the other hand, some may consider it an "error". From mongoose docs, either:

1. err = null， results = []


2. err = null， results = null


3. err =错误文档， results = null

1. err = null, results = []
2. err = null, results = null
3. err = error document, results = null

推荐答案

这取决于查询。如果是 find ，则 results == [] 。如果是 findOne ，则 results == null 。如果一切正常，没有错误。

It depends on the query. If it is a find, then results == []. If it is a findOne, then results == null. No errors if everything else is ok.

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