How do I add expenses for only specific users? - node.js

Question

I have created two models in my app- one for User (_id, email, username, password) and one for Expense (_id, date, detail, amount, category). For the users, I have finished the authentication with jwt.
I want logged-in users to be able to add/remove expenses and not show their expenses to other users but I don't know how I can implement that. I am not asking for code- I would be grateful if you could roughly tell me what I need to do. Thanks!
//expense schema
const expenseSchema = new mongoose.Schema(
{
date: Date,
detail: String,
amount: Number,
category: String
}
)
//controller for adding expenses
const addExpenseController = (req, res) => {
const expense = new Expense({
"date": new Date(),
"amount": req.body.amount,
"detail": req.body.detail,
"category": "expense"
});
expense.save();
res.send('expense added');
};

Answer 1

You should define a ref property in the expense schema pointing at the User model (change the value of the ref attribute to equal the model name given to the users):
const expenseSchema = new mongoose.Schema(
{
...
user: {
type: mongoose.Schema.Types.ObjectId,
ref: 'User'
}
}
)
Then, on creation, specify the user by setting the value of its _id.
You can either store it in the session or pass it in the body, depending on your implementation:
const addExpenseController = async (req, res) => {
try {
const expense = new Expense({
date: new Date(),
amount: req.body.amount,
detail: req.body.detail,
category: 'expense',
user: req.session.user_id, // or req.body.user_id
});
await expense.save();
res.send('expense added');
} catch (err) {
res.send('server error');
}
};