relay-mongoose

About

relay-mongoose is a small library with a few utilities to make implementing relay compliant server easier. It provides a class that enhanced the base mongoose.Model with a few relay helpers.

Usage

EnhancedModel

Use mongoose loadClass() method as described here.

1import * as mongoose from 'mongoose';
2import { EnhancedDocument, EnhancedModel } from 'relay-mongoose';
3
4export interface TestSchemaInterface extends EnhancedDocument {
5	field: string;
6}
7const testSchema = new mongoose.Schema({
8	field: String
9});
10testSchema.loadClass(EnhancedModel);
11
12// Due to the loadClass method implicitly adding new virtual methods to our model
13// To preserve new and old model types for convenience of development the model has to be casted to any
14const TestModel: EnhancedModel<TestSchemaInterface> = mongoose.model('test', testSchema) as any;

You can now use the added findConnections method:

1/* test collection
2[
3    { _id: '1', field: '1' },
4    { _id: '2', field: '2' },
5    { _id: '3', field: '3' },
6]
7*/
8
9const result = await TestModel.findConnections({}, {});
10
11/* result
12{
13  edges: [
14    { node: { id: 'dGVzdC4x', field: '1' }, cursor: 'dGVzdC4x' },
15    { node: { id: 'dGVzdC4y', field: '2' }, cursor: 'dGVzdC4y' },
16    { node: { id: 'dGVzdC4z', field: '3' }, cursor: 'dGVzdC4z' },
17  ],
18  pageInfo: {
19    hasNextPage: false,
20    hasPreviousPage: false,
21    startCursor: 'dGVzdC4x',
22    endCursor: 'dGVzdC4z'
23  }
24}
25*/

Note that the id returned in each node is already a base64 encoded string returned from document.relayId utility.

relayId

As shown in the previous example, all documents returned by findConnections have a modified id which is the base64 encoded concatenation of model name and object ID by a dot.

For example consider the following document in the test collection:

{ _id: '5ea4730dfdea900007758b00', field: 'something' }

Before encoding, relayId value is test.5ea4730dfdea900007758b00. The string is then base64 encoded to mask the collection name in the ID. This value can be decoded by the fromRelayId() utility in relay-mongoose.

This allows to easily write a node query resolver like this:

1import * as mongoose from 'mongoose';
2import { fromRelayId } from 'relay-mongoose';
3
4const Query = {
5	node: (obj, { id }) => {
6		const { modelName, objectId } = fromRelayId(id);
7		return mongoose.models[modelName].findById(objectId);
8	}
9};

findConnections standalone function

There is also a standalone findConnections function to which as the first argument you can pass a mongoose query for more flexibility. For example:

1import * as mongoose from 'mongoose';
2import { EnhancedModel, findConnections } from 'relay-mongoose';
3
4const TestModel: EnhancedModel<any> = mongoose.model('test', testSchema) as any;
5
6const firstQuery = TestModel.find({ condition: 2 }).populate(...);
7const paginatedData = await findConnections(firstQuery, { first: 10 });

Please note that the query passed as the first argument has to have extended the EnhancedModel class as relayId property is needed for correct mapping.

API

EnhancedModel.findConnections

1async findConnections<T extends Document>(
2		conditions: FilterQuery<T>,
3		paginationArgs: PaginationArgs,
4		projection?: any | null
5	): Promise<ConnectionDocuments<T>>

conditions, projection: the same as mongoose find signature arguments.

paginationArgs: pagination arguments as defined by relay specification

1export type Cursor = string;
2
3export interface PaginationArgs {
4	first?: number;
5	last?: number;
6	before?: Cursor;
7	after?: Cursor;
8}
9
10export interface Edge<T> {
11	cursor: Cursor;
12	node: T;
13}
14
15export interface ConnectionDocuments<T> {
16	edges: Edge<T>[];
17	pageInfo: {
18		startCursor?: Cursor;
19		endCursor?: Cursor;
20		hasNextPage: boolean;
21		hasPreviousPage: boolean;
22	};
23}

EnhancedModel.relayId

The base64 encoded concatenation of model name and stringified object ID of a document. Returns a string.

fromRelayId

1type fromRelayId = (id: string) => { modelName: string | null; objectId: string | null };

The reverse operation of EnhancedModel.relayId. Returns null if invalid id is provided.

findConnections

1export const findConnections = async <DocType extends EnhancedDocument, QueryHelpers = {}>(
2	documentQuery: DocumentQuery<DocType | DocType[] | null, any, QueryHelpers> & QueryHelpers,
3	{ before, after, first, last }: PaginationArgs,
4	projection?: any | null
5): Promise<ConnectionDocuments<DocType>>

License

MIT