@adviise/types

Type Safety When Writing and Reading From Firestore

We want to ensure that certain metadata is included in every single document that is created, and updated, so a series of base interfaces have been created for use when creating a new firestore datatype. Adherance to this template will also help ensure data consistency when reading and writing to documents.

Creating A New Firestore Document Type

// import the base interfaces
import { DocData, Metadata, CreateMetadata, UpdateMetadata } from './base';

// Create a generic interface that extends DocData.
// This is where the standard document fields will go.
interface MyDocBase<meta> extends DocData<meta> {
    myField1: string;
    myField2: number;
    myField3: {
        mySubfield: string,
    };
}

// Create a type a new type from this interface that
// passes "Metadata" into the generic slot. This is the type
// you will recieve when fetching from Firestore.
export type MyDocData = MyDocBase<Metadata>;

// create another type but pass in the "CreateMetadata" instead.
// this is the type that you will use when creating a new record
export type MyDocCreateData = MyDocBase<CreateMetadata>;

// Lastly create an interface that extends a Partial
// version of the MyDocBase<UpdateMetadata> and add _metadata: UpdateMetadata
// as a required field. This is the interface that will be used when sending
// update requests
export interface MyDocUpdateData extends Partial<MyDocBase<UpdateMetadata>> {
    _metadata: UpdateMetadata;
}

Using Your New Type

// fetching from firestore
db.collection('my-new-collection').doc('my-id').get().then(doc => {
    // cast doc.data() as MyDocData
    // now you will get autocomplete for doc fields
    const data = doc.data() as MyDocData;
})

// creating a doc
const data: MyDocCreateData = {
    // you will be forced to add all the fields
    // including the _metadata fields here
}
db.collection('my-new-collection').doc('my-id').add(add)

// updating a doc
const updateData: MyDocUpdateData = {
    // you will be forced to add the relevant update _metadata
    // and prevented from adding non-existent fields
    _metadata: {
        updated_at: 'some-timestamp',
        updated_by: 'some-user-id'
    }
    myField1: 'test', // this works
    myNonExistentField: 'test' // this will throw a ts error
}
db.collection('my-new-collection').doc('my-id').update(updateData)