Mongoose Virtual field with async getter - node.js

Question

I have a item model where it a virtual field to refer stock badges.
'use strict';
const mongoose = require('mongoose');
const mongooseHidden = require('mongoose-hidden')();
const Badge = mongoose.model('Badge');
const validateProperty = function(property) {
return (property.length);
};
const Schema = mongoose.Schema;
const ItemSchema = new Schema({
itemCode: {
type: Number,
index: {
unique: true,
sparse: true // For this to work on a previously indexed field, the index must be dropped & the application restarted.
},
required: true
},
itemName: {
type: String,
uppercase: true,
trim: true
},
barcode: {
type: String,
trim: true
},
category: {
type: Schema.Types.ObjectId,
ref: 'Category'
},
subCategory: {
type: Schema.Types.ObjectId,
ref: 'SubCategory'
},
updated: {
type: Date
},
created: {
type: Date,
default: Date.now
},
status: {
type: String,
enum: [
'active', 'inactive', 'removed'
],
default: 'active'
}
}, {id: false});
ItemSchema.virtual('badges').get(function() {
return this.getAvailableBadges();
});
ItemSchema.methods.getAvailableBadges = function() {
Badge.find({
item: this._id
}, (err, badges) => {
if (badges) {
return badges;
} else {
return [];
}
});
};
ItemSchema.set('toJSON', {virtuals: true});
ItemSchema.set('toObject', {virtuals: true});
ItemSchema.plugin(mongooseHidden, {
hidden: {
_id: false,
__v: true
}
});
mongoose.model('Item', ItemSchema);
And batch model as below
'use strict';
const mongoose = require('mongoose');
const mongooseHidden = require('mongoose-hidden')();
const validateProperty = function(property) {
return (property.length);
};
const Schema = mongoose.Schema;
const BadgeSchema = new Schema({
item: {
type: Schema.Types.ObjectId,
ref: 'Item'
},
qty: {
type: Number,
validate: [validateProperty, 'Please enter Quantity !']
},
purchasingPrice: {
type: Number,
validate: [validateProperty, 'Please enter purchasingPrice !']
},
sellingPrice: {
type: Number,
validate: [validateProperty, 'Please enter sellingPrice !']
},
updated: {
type: Date
},
created: {
type: Date,
default: Date.now
},
status: {
type: String,
enum: [
'active', 'inactive', 'removed'
],
default: 'active'
}
});
BadgeSchema.plugin(mongooseHidden, {
hidden: {
_id: false,
__v: true
}
});
mongoose.model('Badge', BadgeSchema);
Item's badge virtual field doesn't got populated.
How are we going to work with async getter method
I have put some console log statements and found that getAvailableBadges is getting data.
I need to send json object with virtual field values via express. How to I do it?

Answer 1

What I did was create an virtual property
ItemSchema.virtual('badges', {
ref: 'Badge',
localField: '_id',
foreignField: 'item'
});
And populate it with
{
path: 'badges',
select: [
'qty', 'purchasingPrice', 'sellingPrice'
],
options: {
sort: {
'created': -1
}
}
}

Answer 2

Well, the operations are asynchronous so you have to wait for the callback to fire.
You can only return the values by passing it in the callback (or you can set the values of the current object prior to calling the callback).
I think it would be something like this:
ItemSchema.virtual('badges').get(function (callback) {
Badge.find({ item: this._id }, callback);
};
Then you would use it like
item.badges(function (err, badges) {
// do something with badges
});