MongoDB-错误:保存之前，文档必须具有_id [英] MongoDB - Error: document must have an _id before saving

问题描述

我在这个项目上一直很努力.我正在跟踪一些领域中已经过时的教程，例如，他们的Jquery版本对某些功能使用了完全不同的格式，因此我不得不做很多改动.但是我认为我要解决的最后一个主要问题是我似乎找不到解决方法.在我的Schema变量中，我有_id，用户名和密码类型

I've been struggling so much with this project. I am following a tutorial that is out of date in some areas, for instance their version of Jquery used a totally different format for some functions and I had to do a lot of changing around. But I think I am down to one last major problem that I can't seem to find a fix for. In my Schema variable I've got the _id, username, and password types

var UserSchema = new mongoose.Schema({
    _id: mongoose.Schema.ObjectId,
    username: String,
    password: String
}); 

但是当我尝试向应用程序中添加新用户时，它没有弹出我应该得到的警报，而是弹出为[object Object]，并且没有任何内容添加到数据库中.然后在mongo cmd中弹出此错误

but when I go to try to add a new user to my app, instead of getting the alert I am supposed to get, it pops up as [object Object] and nothing gets added to the database. Then this error pops up in the mongo cmd

错误:文档在保存之前必须具有_id".

"Error: document must have an _id before saving".

我尝试注释掉_id行，并且得到了正确的消息，但是数据库中仍然没有任何内容.

I've tried commenting out the _id line and I get the right message but still nothing shows up in my database.

推荐答案

非常简单:

1. 如果已在架构中显式声明_id字段，则必须显式初始化
2. 如果您尚未在架构中声明它，则MongoDB将对其进行声明和初始化.

您不能做的是将其包含在架构中，而不初始化它.它将引发您正在谈论的错误

What you can't do, is to have it in the schema but not initialize it. It will throw the error you are talking about

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