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javascript - 尝试使用 Mongoose 时出现 MongoClient 未连接错误？

问题描述

作为我课程的一部分，我正在学习 mongodb，现在正在学习 Mongoose。我已经完全按照课程中的方式编写了代码，但是当尝试使用 node app.js 启动它时，我收到以下错误：

$ node app.js (node:25772) UnhandledPromiseRejectionWarning: MongoNotConnectedError: MongoClient must be connected to perform this operation at Object.getTopology (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\node_modules\mongodb\lib\utils.js:391:11) at Collection.insertOne (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\node_modules\mongodb\lib\collection.js:150:61) at NativeCollection.<computed> [as insertOne] (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\drivers\node-mongodb-native\collection.js:200:33) at NativeCollection.Collection.doQueue (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\collection.js:135:23) at C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\collection.js:82:24 at processTicksAndRejections (internal/process/task_queues.js:77:11) (Use node --trace-warnings ... to show where the warning was created) (node:25772) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag--unhandled-rejections=strict (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1) (node:25772) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

我在终端的单独选项卡中运行了 mongosh，我尝试了几次搜索来寻找类似的问题。非常欢迎任何帮助！

这是我的完整 app.js 代码：



mongoose.connect("mongodb://localhost:27017/fruitsDB");


const fruitSchema = new mongoose.Schema({
  name: String,
  rating: Number,
  review: String
});

const Fruit = mongoose.model("Fruit", fruitSchema);

const fruit = new Fruit({
  name: "Apple",
  rating: 7,
  review: "Pretty solid as a fruit"
});

fruit.save();
mongoose.connection.close();


const findDocuments = function(db, callback) {

  const collection = db.collection('fruits');

  collection.find({}).toArray(function(err, fruits) {
    assert.equal(err, null);
    console.log("Found the following records");
    console.log(fruits)
    callback(fruits);

  });
}

标签： javascriptmongodbmongoose

解决方案

mongoose.connect是异步的，因此您尝试在与数据库建立连接之前执行代码。

const connectToMongo = async() => {
    await mongoose.connect("mongodb://localhost:27017/fruitsDB", {
        useNewUrlParser: true,
        useUnifiedTopology: true,
        useFindAndModify: false,
    });
    return mongoose;
};

您现在可以使用 async/await 或 .then() 等待连接建立

(async function () {
    await connecToMongo();

    const fruitSchema = new mongoose.Schema({
        name: String,
        rating: Number,
        review: String
    });

    const Fruit = mongoose.model("Fruit", fruitSchema);

    const fruit = new Fruit({
        name: "Apple",
        rating: 7,
        review: "Pretty solid as a fruit"
    });

    fruit.save();
    mongoose.connection.close();


    const findDocuments = function (db, callback) {

        const collection = db.collection('fruits');

        collection.find({}).toArray(function (err, fruits) {
            assert.equal(err, null);
            console.log("Found the following records");
            console.log(fruits)
            callback(fruits);

        });
    }
})

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