cross-database populate not working

[ayalhus]

Trying to populate postDB collection with user's information from userDB:

`mongoose.connect("mongodb://localhost:27017/userDB", { useNewUrlParser: true, useUnifiedTopology: true });
mongoose.set("useUnifiedTopology", true);
mongoose.set("useCreateIndex", true);

const postDbConnection = mongoose.createConnection('mongodb://localhost:27017/postDB', { useNewUrlParser: true });

const userSchema = new mongoose.Schema({

email: String,
password: String,
googleId: String,
posts: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Post' }]
});

const postSchema = new mongoose.Schema({
title: String,
content: String,
created:
{type: Date, default: Date.now},
user: [{ type: mongoose.Schema.Types.ObjectId, ref: User, required: true }]
});

userSchema.plugin(passportLocalMongoose);
userSchema.plugin(findOrCreate);

// this uses the default connection (to userDB)
const User = new mongoose.model("User", userSchema);

// this uses the second connection (to postDb)
const Post = postDbConnection.model('Post', postSchema);`

I get the following error:

Cannot access 'User' before initialization

Unless I use
ref: 'User'
instead of
ref: User
Which is not the correct way to refer to a model name from an outside connection

[vkarpov15]

Use 'User'. Both ways are correct depending on context, but in this case you can't use ref: User because User isn't defined when you're trying to use it.