Mongoose Typescript Class

Question

The class below throws the error

Type 'typeof import("mongoose")' is missing the following properties from type 'Db': serverConfig, bufferMaxEntries, databaseName, options, and 37 more.

I cannot find out what the return type of mongoose.connect is.

import mongoose from "mongoose";
import {Db} from "mongodb";

interface MongoDbConfig {
   server: String, 
   port: String,
   dbName: String;
} 
// TODO: make singelton
class MongoDb {
    private db : Db;
    private _server : String;
    private _port : String;
    private _dbName : String;

    constructor(config: MongoDbConfig){
            this._server = config.server;
            this._port = config.port;
            this._dbName = config.dbName

    }

    public async connect() {
        const uri = "mongodb://"+this._server+":"+this._port+"/"+this._dbName;
        this.db = await mongoose.connect(uri, { useNewUrlParser: true }); // error
        console.log(typeof this.db)
        console.log("Connected to db");
        return this.db;
    }

    public getDb(){
        return this.db;
    }
}

deerawan · Accepted Answer · 2020-01-25 00:37:41Z

2

The issue seems comes from typing declaration in the code for db variable. The type definition mentioned that the connect function returns Promise<Mongoose> but this.db has Db type instead of Mongoose.

This may solve the issue

private db: mongoose.Mongoose; // change from Db to mongoose.Mongoose

// ...

this.db = await mongoose.connect(uri, { useNewUrlParser: true });

Hope it helps

answered Jan 25, 2020 at 0:37

deerawan

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Limboer · Accepted Answer · 2020-01-24 18:08:04Z

I checked the doc: here is what it is saying:

The connect() function also accepts a callback parameter and returns a promise.

mongoose.connect(uri, options, function(error) {
  // Check error in initial connection. There is no 2nd param to the callback.
});

// Or using promises
mongoose.connect(uri, options).then(
  () => { /** ready to use. The `mongoose.connect()` promise resolves to mongoose instance. */ },
  err => { /** handle initial connection error */ }
);

As you see, it actually return a promise, and this promise resolves to mongoose instance

I checked the mongoose's index.d.ts as well, what I find is:

/**
 * Opens the default mongoose connection.
 * Options passed take precedence over options included in connection strings.
 * @returns pseudo-promise wrapper around this
 */
export function connect(uris: string, options: ConnectionOptions, callback: (err: mongodb.MongoError) => void): Promise<Mongoose>;
export function connect(uris: string, callback: (err: mongodb.MongoError) => void): Promise<Mongoose>;
export function connect(uris: string, options?: ConnectionOptions): Promise<Mongoose>;

So it looks it it returning Promise<Mongoose> and since you are using async/await, the resolve value will just be Mongoose.

Bye the way, not sure what you are doing here, but i would recommend just follow as the doc says when connecting to database:

mongoose.connect('mongodb://localhost/test', { useNewUrlParser: true });
const db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
  console.log('Successfully connected to db')
});

Your this.db probably should equal to mongoose.connection which having a type of mongoose.Connection, rather than the resolve result of mongoose.connect(...)?

Hope this helps.

Anonymous Creator · Accepted Answer · 2021-03-31 15:28:58Z

0

You can use it as below.

import { connect, Mongoose } from 'mongoose';
//...
private db: Mongoose;
//...
this.db = await connect(uri, { useNewUrlParser: true });

answered Mar 31, 2021 at 15:28

Anonymous Creator

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