使用 mongo 客戶端異步訪問 mongo 集合時出錯

Question

我已經構建了以下 mongo 客戶端訪問引導程序文件：

import { MongoClient } from "mongodb";

let db = null;

// Connect to mongo
const uri = "mongodb://localhost/mydb";
const opts = { useUnifiedTopology: true };

const connect = async () => {
    console.log("Connecting to database...");

    let client = await MongoClient.connect(uri, opts).catch(error => {
        console.log("Error connecting to database: " + err);
    });

    if (client) {
        console.log("Database connected.");
        db = client.db("mydb");
    }

    return client;
};

// Get database connection
const getDb = async () => {
    if (!db) await connect();

    return db;
};

// Get Collection
const getCollection = async name => {
    let database = await getDb();

    let collection = await database.collection(name);

    if (!collection)
        throw new Error("(mongo) Cannot get collection named " + name);

    return collection;
};

export { db, getCollection };

在另一個程序中第一次嘗試訪問集合時：

import { getCollection } from "./mongoutils";

const init = async () => {
    let user = await getCollection("users").findOne({ name: "Josh"});

    console.log("User found!");
}

我收到以下錯誤：

UnhandledPromiseRejectionWarning: TypeError: (0 , _mongo.getCollection)(...).findOne is not a function

如何正確修復此錯誤，保持整個結構async/await ？

Answer 1

異步函數返回一個承諾而不是解析的數據。

這里getCollection()是一個異步函數。 因此，調用getCollection("users")將返回一個承諾，而不是解析集合本身，因為我假設您期望的是什么。 正確的做法是：

import { getCollection } from "./mongoutils";

const init = async () => {
    let userCollection = await getCollection("users");
    try {
      let user = await userCollection.findOne({ name: "Josh"})
      console.log("User found!");
    } catch (e) { 
      console.log("User not found!");
    }
}