Virtual in Mongoose Object is Undefined? - node.js

Question

I've been picking up MongoDB and Mongoose recently in an effort to learn the MEAN stack. Using this course: https://www.edx.org/course/introduction-mongodb-using-mean-stack-mongodbx-m101x I am attempting to create a virtual for my product schema that displays the price in a more user-friendly way. However, when printing out this virtual displayPrice it comes up as undefined unless accessed through toObject or toJSON and even then the USD symbol appears as a question mark. I apologize for any stupidity and obvious overlooks, I am new to this database stuff and can't find many tutorials that explain things simply.
Here is the code:
var mongoose = require("mongoose");
var Category = require("./categoryschema.js");
var productSchema = {
name: {
type: String,
required: true
},
// Pictures must start with http://"
pictures: [{ type: String, match: /^http:\/\//i }],
price: {
amount: {
type: Number,
required: true
},
currency: {
type: String,
enum: ["USD", "EUR", "GBP"],
required: true
}
},
category: Category.categorySchema
};
module.exports = new mongoose.Schema(productSchema);
module.exports.productSchema = productSchema;
var schema = new mongoose.Schema(productSchema);
var Product = mongoose.model("Product", schema);
var currencySymbols = {
"USD": "$",
"EUR": "E",
"GBP": "P"
};
// Make human readable string form of price. "$25" instead of "25 USD"
schema.virtual("displayPrice").get(function() {
return currencySymbols[this.price.currency] + "" + this.price.amount;
});
schema.set("toObject", { virtuals: true });
schema.set("toJSON", { virtuals: true });
var p = new Product({
name: "test product",
price: {
amount: "33.58",
currency: "USD"
}
});
console.log(p.displayPrice);
p.price.amount = 20;
console.log(p.displayPrice);
p.price.currency = "EUR";
console.log(JSON.stringify(p));
var obj = p.toObject();
console.log(obj.displayPrice);
Output:
undefined
undefined
{"name":"test product","_id":"569c39774093336c149eba2c","category":{"ancestors":
[]},"price":{"amount":20,"currency":"EUR"},"pictures":[],"displayPrice":"E20","i
d":"569c39774093336c149eba2c"}
E20

Answer 1

The only thing that seemed to work is assigning the virtual to the price key. I have no idea why this was the solution so any answer would be appreciated. It only seemed to change directly logging the virtual's value.
New productSchema:
var mongoose = require("mongoose");
var Category = require("./categoryschema.js");
var fx = require("./fx.js");
var productSchema = {
name: {
type: String,
required: true
},
// Pictures must start with http://"
pictures: [{ type: String, match: /^http:\/\//i }],
price: {
amount: {
type: String,
required: true,
set: function(v) {
this.internal.approximatePriceUSD = v / (fx()[this.price.currency] || 1);
return v;
}
},
currency: {
type: String,
enum: ["USD", "EUR", "GBP"],
required: true,
set: function(v) {
this.internal.approximatePriceUSD = this.price.amount / (fx()[v] || 1);
return v;
}
}
},
category: Category.categorySchema,
internal: {
approximatePriceUSD: Number
}
};
var schema = new mongoose.Schema(productSchema);
var Product = mongoose.model("Product", schema);
var currencySymbols = {
"USD": "$",
"EUR": "E",
"GBP": "P"
};
// Make human readable string form of price. "$25" instead of "25 USD"
schema.virtual("price.displayPrice").get(function() {
return currencySymbols[this.price.currency] + "" + this.internal.approximatePriceUSD;
});
schema.set("toObject", { virtuals: true });
schema.set("toJSON", { virtuals: true });
var p = new Product({
name: "test product",
price: {
amount: "12.50",
currency: "USD"
},
category: {
name: "test"
}
});
console.log(p.price.displayPrice);
console.log(p.price.currency + ": " + p.internal.approximatePriceUSD);
p.price.currency = "EUR";
console.log(p.price.displayPrice);
console.log(p.price.currency + ": " + p.internal.approximatePriceUSD);
p.price.currency = "GBP";
console.log(p.price.displayPrice);
console.log(p.price.currency + ": " + p.internal.approximatePriceUSD);
module.exports = new mongoose.Schema(productSchema);
module.exports.productSchema = productSchema;
New output:
$12.5
USD: 12.5
E11.363636363636363
EUR: 11.363636363636363
P8.333333333333334
GBP: 8.333333333333334