Joining collections in mongodb with node js - node.js

Question

I have two collections in mongodb "components" and "airframes" which I am trying to join together (with a one to many relationship). I have the following code which gets the airframe and component data separately from the database, however after days of effort, I cannot figure out how to join the two together. I assume I need to use $lookup to achieve the desired result but any assistance in constructing the code would be greatly appreciated.
my models are as follows and I am trying to join all the component records under the associated Airframe. the airframe field on the Component holds the related Airframes' id.
const airframeSchema = mongoose.Schema({
name: { type: String, required: true },
sNumber: { type: String, required: true },
aStatus: { type: String, required: true },
components: [ {
type: mongoose.Schema.Types.ObjectId,
ref: 'Component' } ]
});
module.exports = mongoose.model('Airframe', airframeSchema);
const componentSchema = mongoose.Schema({
name: { type: String, required: true },
serial: { type: String, required: true },
type: { type: String, required: true },
airFrame: {
type: mongoose.Schema.Types.ObjectId,
required: true,
ref: 'Airframe'},
});
module.exports = mongoose.model('Component', componentSchema);
the AirFramesService is as follow. I would like to join the component data under a array called "component".
getAirframes() {
this.http
.get<{ message: string; airframes: any }>("http://3.135.49.46:8080/api/airframes")
.pipe(
map(airframeData => {
return airframeData.airframes.map(airframe => {
return {
name: airframe.name,
sNumber: airframe.sNumber,
aStatus: airframe.aStatus,
id: airframe._id,
};
});
})
)
.subscribe(transformedAirframes => {
this.airframes = transformedAirframes;
this.airframesUpdated.next([...this.airframes]);
});
}
getAirframeUpdateListener() {
return this.airframesUpdated.asObservable();
}
getAirframe(id: string) {
return this.http.get<{ _id: string; name: string; sNumber: string ; aStatus: string}>(
"http://3.135.49.46:8080/api/airframes/" + id
);
}
The airframes route code is as follows:
router.get("", (req, res, next) => {
Airframe.find().then(documents => {
res.status(200).json({
message: "Airframes fetched successfully!",
airframes: documents
});
});
});
and here is the code within the ts component file that gets the airframe data is as follows.
constructor( public airframesService: AirframesService) {
this.airframesService.getAirframes();
this.airframesSub = this.airframesService.getAirframeUpdateListener()
.subscribe((airframes: Airframe[]) => {
this.isLoading = false;
this.airframes = airframes;
}, 0);
});
}
the desired outcome would be the following (at the moment I only get the airframe data):
{
_id: "123"
name: "Airframe01"
sNumber: "757"
aStatus: "Active"
id: "5e8052ad1fa18f1c73524664"
components: [
{
name: "Left Tank",
serial: "3456789",
type: "Landing Gear",
airFrame: "5e8052ad1fa18f1c73524664"
},
{
name: "Right Tank",
serial: "45678",
type: "Landing Gear",
airFrame: "5e8052ad1fa18f1c73524664"
}
]
}

Answer 1

Your document structure already established a one-to-many kinda relationship between the two models, you can use Mongoose population to get the join you described in the question. The populate code should be somewhere in the airframes route like this:
router.get("", (req, res, next) => {
// Notice the populate() method chain below
Airframe.find().populate('components').then(documents => {
// The documents output should have their "components" property populated
// with an array of components instead of just Object IDs.
res.status(200).json({
message: "Airframes fetched successfully!",
airframes: documents
});
});
});
You can read more about Mongoose population here.