node.js 如何使用猫鼬 findOne
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How to use mongoose findOne
提问by Callum Rogers
I have the below schema (apologies that it is in coffeescript)
我有以下模式（抱歉，它是在 coffeescript 中）
Schema = mongoose.Schema
AuthS = new Schema
auth: {type: String, unique: true}
nick: String
time: Date
Auth = mongoose.model 'Auth', AuthS
I simply want to recover one record which is definitely in my database:
我只想恢复一条肯定在我的数据库中的记录：
Auth.findOne({nick: 'noname'}, function(obj) { console.log(obj); });
Unfortunately this always logs null. db.auths.findOne({nick: 'noname'})in mongo shell always returns a value. What is going on?
不幸的是，这总是记录null。db.auths.findOne({nick: 'noname'})在 mongo shell 中总是返回一个值。到底是怎么回事？
回答by Callum Rogers
Found the problem, need to use function(err,obj)instead:
发现问题，需要function(err,obj)改用：
Auth.findOne({nick: 'noname'}, function(err,obj) { console.log(obj); });
回答by Isaac Pak
Mongoose basically wraps mongodb's api to give you a pseudo relational db api so queries are not going to be exactly like mongodb queries. Mongoose findOnequery returns a query object, not a document. You can either use a callback as the solution suggests or as of v4+ findOnereturns a thenable so you can use .then or await/async to retrieve the document.
Mongoose 基本上包装了 mongodb 的 api，为您提供一个伪关系数据库 api，因此查询不会与 mongodb 查询完全一样。Mongoose findOne查询返回一个查询对象，而不是一个文档。您可以按照解决方案的建议使用回调，或者从 v4+ findOne 开始返回 thenable，以便您可以使用 .then 或 await/async 来检索文档。
// thenables
Auth.findOne({nick: 'noname'}).then(err, result) {console.log(result)};
Auth.findOne({nick: 'noname'}).then(function (doc) {console.log(doc)});
// To use a full fledge promise you will need to use .exec()
var auth = Auth.findOne({nick: 'noname'}).exec();
auth.then(function (doc) {console.log(doc)});
// async/await
async function auth() {
const doc = await Auth.findOne({nick: 'noname'}).exec();
return doc;
}
auth();
See the docsif you would like to use a third party promise library.
如果您想使用第三方承诺库，请参阅文档。
回答by Bhagvat Lande
In my case same error is there , I am using Asyanc / Await functions , for this needs to add AWAIT for findOne
在我的情况下，存在同样的错误，我使用的是 Asyanc/Await 函数，为此需要为 findOne 添加 AWAIT
Ex:const foundUser = User.findOne ({ "email" : req.body.email });
above , foundUser always contains Object value in both cases either user found or not because it's returning values before finishing findOne .
上面，在两种情况下，foundUser 始终包含 Object 值，无论用户是否找到，因为它在完成 findOne 之前返回值。
const foundUser = await User.findOne ({ "email" : req.body.email });
above , foundUser returns null if user is not there in collection with provided condition . If user found returns user document.
上面，如果用户不在集合中并提供条件，则 foundUser 返回 null。如果用户找到，则返回用户文档。
回答by Neil Guy Lindberg
You might want to consider using console.logwith the built-in "arguments" object:
您可能需要考虑使用console.log内置的“参数”对象：
console.log(arguments); // would have shown you [0] null, [1] yourResult
This will always output all of your arguments, no matter how many arguments you have.
无论您有多少个参数，这将始终输出您的所有参数。
回答by NaturalCoder
Use obj[0].nick and you will get desired result,
使用 obj[0].nick 你会得到想要的结果，
