Reference Collections

Firebase allows you to reference documents of other collections.

Consider the example below of Person and Anddress

@FirebaseCollection()
class Address {
    @DocumentKey(DocumentKeyType.UserDefined)
    addrKey: String = "";

    @DocumentField
    streetName?: String;

    @DocumentField
    houseNumer?: String;
}

The Person document has a address field that stores reference to the address

@FirebaseCollection()
class Person{

    @DocumentKey(DocumentKeyType.UserDefined)
    name: String;

    @DocumentField
    age: Number;

    location?: String;

    @DocumentField
    phone: String;

    @DocumentField
    homeAddress?: Address;

    constructor(name: String){
        this.name = name;
    }

}

Create Document

Create the address by the normal method.

const addressCollection = jugnu.createFirebaseCollection(Address);

const addr = new Address();
addr.addrKey = "Varun-Addr";
addr.streetName = "My Street Address";
addr.houseNumer = "My House No";
addressCollection.create(addr);     // Create new Address

Create person, with reference to Address.

const personCollection = jugnu.createFirebaseCollection(Person);

const varun = new Person("Varun Verma");
varun.age = 25;
varun.location = "India";
varun.phone = "+91-1234567890";
varun.homeAddress = addr;           // Set address in Person

personCollection.create(varun); 

The person document is created with Address as a reference document

Creating Document with collection of references

We have seen how to store the refence of other documents. Sometimes, we have to store a collection of document references.

For e.g. store a list of many children in a Person Profile.

@FirebaseCollection()
class Person {
    @DocumentKey(jugnu.Types.DocumentKeyType.UserDefined)
    id: string;

    @DocumentField
    name: string;

    @DocumentField
    parent: Person;     // Reference to Self Collection

    @DocumentArrayField(Person)
    children: Person[];   // Reference to Self Collection

    constructor(id: string){
        this.id = this.name = id;
        this.children = [];
    }
}

const createFunction = async() => { 

    const vv = new Person("Varun");

    vv.parent = new Person("Papa");

    const beta = new Person("Beta");
    const beti = new Person("Beti");

    vv.children.push(beta);
    vv.children.push(beti);

    const id = await personCollection.create(vv);
    console.log(vv);

};

The peron document is created with references

Query Single Document with Key

Querying document will also query the referenced documents and populate their properties.

let p: Person;
p = await personCollection.getDocument("Varun Verma");
console.log("Person Details", p);

The output will be:

Person {
  age: 25,
  phone: '+91-1234567890',
  homeAddress: {
    houseNumer: 'My House No',
    addrKey: 'Varun-Addr',
    streetName: 'My Street Address'
  },
  name: 'Varun Verma'
}

Get Reference of the document

To get a reference of the document :

const addr = new Address("Home");
const addressRef = addressCollection.getReference(addr);

Delete Document

Delete will delete only the main document. The referenced document will not be deleted.