猫鼬Model.findOne TypeError:对象没有方法'findOne' [英] mongoose Model.findOne TypeError: Object has no method 'findOne'

问题描述

我有一个简单的node.js代码，它使用猫鼬在保存时有效，但无法检索.

I have a simple node.js code that uses mongoose which works when saving but doesn't retrieve.

.save()有效，但.findOne()无效.

mongoose = require('mongoose');
mongoose.connect("mongodb://localhost/TestMongoose");
UserSchema = new mongoose.Schema({
    field: String
    });
Users = mongoose.model('userauths', UserSchema);

user = new Users({
    field: 'value'
    });

//user.save();  

^有效.即使用值更新数据库. 屏幕截图

^ works. i.e. updates the database with values. screenshot

//user.findOne({field:'value'},function(err,value){});

^引发错误:

user.findOne({field:'value'},function(err,value){});
     ^
TypeError: Object { field: 'value', _id: 52cd521ea34280f812000001 } has no method 'findOne'
    at Object.<anonymous> (C:\localhost\nodeTest\z.js:16:6)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:901:3

---

console.log(JSON.stringify(   user    , null, 40));

^仅返回对象{field: 'value'}

console.log(JSON.stringify(   Users   , null, 40));

^返回undefined

Users.findOne();

^没有错误，但不返回任何内容.
(所以Users中是否存在函数findOne()?但是为什么console.log(..Users..返回undefined?)

^ no error, but doesn't return anything.
(so does the function findOne() exists in Users? but so why then does console.log(..Users.. returns undefined?)

什么可能导致findOne()无法按预期工作?

What could be the issue causing findOne() to not work as expected?

推荐答案

findOne 是Users模型上的方法，而不是user模型实例上的方法.它通过回调将其异步结果提供给调用方:

findOne is a method on your Users model, not your user model instance. It provides its async results to the caller via callback:

Users.findOne({field:'value'}, function(err, doc) { ... });

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