Passing an argument from Model.prototype.METHOD to Schema.prototype.pre() methods?

[samislam]

I need to pass an argument from the Model.prototype.create() method to the Schema.prototype.pre('validate') method somehow?
Is there any way I can do it?
I need for example to do that in multiple places, I need for instance to pass the express request object to Mongoose, I.e.: passing an argument from the controller to the model.

My case:

TransactionModel.create({
  from: req.body.from, // id (user object id)
  to: req.body.to, // id (user object id)
  amount: req.body.amount // number, ex: 20$
})

const TransactionSchema = new mongoose.Schema({
from: new mongoose.Schema({ name: String, age: Number, balance: Number }),
to: new mongoose.Schema({ name: String, age: Number, balance: Number }),
amount: Number // the amount of money to transfer
})

TransactionSchema.pre('save', function(){
   const doc = this
   const fromDoc = await UserMode.findById(doc.from) // to save the user document itself instead of the reference id
   const toDoc = await UserMode.findById(doc.to) // to save the user document itself instead of the reference id
  fromDoc.deductBalance(doc.amount)
  toDoc.feedBalance(doc.amount)
})

The problem is that Mongoose is complaining that Casting to Embedded failed.

How to pass an argument from my express controllers to Mongoose (I call it the model because I use MVC) without validations?

*** for reference: here's the UserModel:

const UserSchema = new mongoose.Schema({
  name: String,
  age: Number,
  balance: Number,
  email: {
     type: String,
     required: [true, "a user must have an email address"]
  }
})

UserSchema.methods.deductBalance = async function (amount){
  const doc = this
  doc.balance = doc.balance -  amount;
  return await doc.save()
}

UserSchema.methods.feedBalance = async function (amount){
  const doc = this
  doc.balance = doc.balance +  amount;
  return await doc.save()
}

[vkarpov15]

Set the values you want to pass on $locals, that's where you can store any extra data you want associated with your document that you don't want stored in MongoDB.

const t = new TransactionModel({
  amount: req.body.amount // number, ex: 20$
})
t.$locals.from = req.body.from; // id (user object id)
t.$locals.to = req.body.to; // id (user object id)
await t.save();

// In pre()
TransactionSchema.pre('save', function(){
   const doc = this
   const fromDoc = await UserMode.findById(doc.$locals.from) // to save the user document itself instead of the reference id
   const toDoc = await UserMode.findById(doc.$locals.to) // to save the user document itself instead of the reference id
  fromDoc.deductBalance(doc.amount)
  toDoc.feedBalance(doc.amount)
})

[samislam]

Good. Can I use this concept to translate the Mongoose custom validation error messages as well?
For instance:

const xSchema = new mongoose.Schema({
age: {
  type: String,
  required: [true, req.body.lang === "en"? "Age is required" : "يرجى ادخال العمر"],
}
})

How I can translate these messages if the
Desired language is determined in the request object?

[vkarpov15]

You can set lang on the document's $locals. Or just the entire req:

const t = new TransactionModel({
  amount: req.body.amount // number, ex: 20$
})
t.$locals.req = req;
await t.save();

[samislam]

And how to translate the validation message afterwards? Using middlewares?

[vkarpov15]

@samislam yes, currently you would have to use error handling middleware. xSchema.post('save', function(err, res, next) { if (err instanceof mongoose.Error.ValidationError) { ... } }). We'll add an issue to allow transforming error message based on document