apollo/docs/source/tutorial/data-source.md

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2. Hook up your data sources	Start here for the Apollo fullstack tutorial

Apollo data sources provide the best experience for fetching and caching data from REST endpoints, web services, and databases. It's a new pattern for loading data from various sources, with built-in support for deduplication, caching, and error handling.

Connect a REST API

To get started connecting to a REST API, install the apollo-datasource and apollo-datasource-rest packages:

npm install apollo-datasource-rest

The apollo-datasource-rest exposes the RESTDataSource class that is responsible for fetching data from a given REST API. To define a data source for the REST endpoint, extend the RESTDataSource class and implement the data fetching methods that your resolvers require. Let's look at a simple example to understand how data sources work.

import { RESTDataSource } from 'apollo-datasource-rest';

export class MvrpAPI extends RESTDataSource {
  constructor() {
    super();
    this.baseURL = 'https://mvrp.herokuapp.com/api/';
  }

  async getAllCars() {
    return this.get('cars');
  }

  async getACar(plateNumber) {
    const result = await this.get('car', {
      plateNumber
    });

    return result[0];
  }
};

The https://mvrp.herokuapp.com/api/ endpoint is a simple REST API that returns data for cars.

The MvrpAPI class implementation in the code above contains a getAllCars and getACar functions that wrap convenience methods provided by the RESTDataSource class for performing HTTP requests. In this example, we used the built-in get method that's responsible for GET requests.

Connect a database