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Connect to database
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unicodeveloper
committed by
Peggy Rayzis
Peggy Rayzis
parent
d1400b5659
commit
05e0bd88c1
@@ -7,18 +7,19 @@ Apollo data sources provide the best experience for fetching and caching data fr
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<h2 id="rest-api">Connect a REST API</h2>
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To get started connecting to a REST API, install the `apollo-datasource` and `apollo-datasource-rest` packages:
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To get started, install the `apollo-datasource` and `apollo-datasource-rest` packages:
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```bash
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npm install apollo-datasource-rest
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npm install apollo-datasource apollo-datasource-rest --save
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```
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The `apollo-datasource-rest` package 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.
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* **apollo-datasource**: This is the generic data source package. It's good for connecting to non-REST data sources.
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* **apollo-datasource-rest**: This package 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.
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```js
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import { RESTDataSource } from 'apollo-datasource-rest';
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const { RESTDataSource } = require('apollo-datasource-rest');
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export class MvrpAPI extends RESTDataSource {
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class MvrpAPI extends RESTDataSource {
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constructor() {
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super();
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this.baseURL = 'https://mvrp.herokuapp.com/api/';
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@@ -36,6 +37,8 @@ export class MvrpAPI extends RESTDataSource {
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return result[0];
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}
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};
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module.exports = MvrpAPI;
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```
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The `https://mvrp.herokuapp.com/api/` endpoint is a simple REST API that returns data for cars. Furthermore, 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, the built-in `get` method used is responsible for `GET` requests.
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@@ -142,4 +145,239 @@ async getLaunchesByIds({ launchIds }) {
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The `getLaunchById` method takes in a flight number and returns the data for a particular launch, while `getLaunchesByIds` returns several launches based on their respective `launchIds`. `Promise.all()` takes an array of promises and returns a single promise that resolves when all the promises in the array have been resolved with their fulfilled values.
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<h2 id="database">Connect a database</h2>
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<h2 id="database">Connect a database</h2>
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A data store is needed for saving and fetching user information. It's also important for user trips. Let's make use of [SQLite](https://www.sqlite.org) for our app's database. SQLite is a self-contained, light-weight, zero-configuration and embedded SQL database engine.
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Before connecting to SQLite, go ahead and install `sequelize`:
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```bash
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npm install sequelize --save
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```
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**Sequelize** is an ORM for Node.js that supports several relational database management systems such as MySQL, MariaDB, PostgreSQL, SQLite and MSSQL. In this tutorial, we'll make use of it for the SQLite database.
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Now, create a `store.sqlite` file in the root directory. Once you have done that, change the directory from root to `src/datasources`:
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```bash
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cd src/datasources
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```
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Create a `user.js` file inside the `src/datasources` directory. We'll connect to the sqlite database and set up the methods for interacting with the SQL data source within the `src/datasources/user.js` file. Time to set up!
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_src/datasources/user.js_
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```js
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const { DataSource } = require('apollo-datasource');
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const SQL = require('sequelize');
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class UserAPI extends DataSource {
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constructor() {
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super();
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this.store = createStore();
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}
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}
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const createStore = () => {
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const Op = SQL.Op;
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const operatorsAliases = {
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$in: Op.in,
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};
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const db = new SQL('rocket', null, null, {
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dialect: 'sqlite',
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storage: './store.sqlite',
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operatorsAliases,
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});
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};
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module.exports = UserAPI;
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```
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In the code above, the `createStore` function sets up a new SQL instance that connects to the SQLite database with the name of the database specified which is `rocket`. Username and password are null, the location and operator aliases are also required.
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The `createStore` function is also invoked in the constructor and stored in a class variable called `store`.
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Let's extend the `createStore` function to create a `users` and `trips` table.
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```js
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...
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...
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const createStore = () => {
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...
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const users = db.define('user', {
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id: {
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type: SQL.INTEGER,
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primaryKey: true,
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autoIncrement: true,
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},
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createdAt: SQL.DATE,
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updatedAt: SQL.DATE,
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email: SQL.STRING,
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token: SQL.STRING,
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});
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const trips = db.define('trip', {
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id: {
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type: SQL.INTEGER,
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primaryKey: true,
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autoIncrement: true,
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},
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createdAt: SQL.DATE,
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updatedAt: SQL.DATE,
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launchId: SQL.INTEGER,
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userId: SQL.INTEGER,
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});
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return { users, trips};
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};
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```
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The `users` and `trips` tables have now been defined with their respective fields. And an object containing `users` and `trips`is returned within the `createStore` function to enable us access the ORM methods later on in the body of our data source.
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Now that we are done with the table creation, let's set up methods in the `UserAPI` class to:
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* Create a user.
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* Book a trip.
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* Cancel a trip.
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* Get launches reserved by a user.
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* Get all the users that have reserved a particular launch.
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### Create a User
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Head over to your terminal and install the `isemail` package:
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```bash
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npm install isemail --save
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```
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The `isemail` package is an npm module that validates emails. Now, write the code to find or create a user below:
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_src/datasources/user.js_
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```js
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const { DataSource } = require('apollo-datasource');
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const SQL = require('sequelize');
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const isEmail = require('isemail');
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class UserAPI extends DataSource {
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constructor() {
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super();
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this.store = createStore();
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}
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userReducer(user) {
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return {
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id: user.id,
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email: user.email,
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avatar: user.avatar,
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};
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}
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async findOrCreateUser({ email }) {
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if (!isEmail.validate(email)) return null;
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const users = await this.store.users.findOrCreate({ where: { email } });
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return users && users[0] ? this.userReducer(users[0]) : null;
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}
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}
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....
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// the createStore function is here
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....
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module.exports = UserAPI;
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```
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The `userReducer` method makes the `UserAPI` class easier to test because it abstracts the user object been returned from the `findOrCreateUser` method into a different method.
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The `findOrCreateUser` method takes in a user's email and checks whether the email argument is a valid email address. If it's not valid, null is returned, else it runs a check within the `users` table in the SQLite database. If the email exists in the database, then the user already exists, else a new user is created, stored in the database.
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### Book and Cancel a Trip
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Add a `bookTrip` and `cancelTrip` method to the `UserAPI` data source class.
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_src/datasources/user.js_
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```js
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...
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class UserAPI extends DataSource {
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constructor() {
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...
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}
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...
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async bookTrip({ userId, launchId }) {
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return this.store.trips.findOrCreate({ where: { userId, launchId } });
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}
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async cancelTrip({ userId, launchId }) {
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return this.store.trips.destroy({ where: { userId, launchId } });
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}
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}
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...
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```
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A user selects a particular launch and books a trip. The `userId` and `launchId` values are needed to book the trip successfully. Therefore, the `bookTrip` method invokes the `findOrCreate` method on the `trips` table to book the trip.
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The `cancelTrip` method requires a `userId` and `launchId` to delete a trip from the `trips` table successfully.
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### Get Launches and Users
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We need to get all the launches reserved by a user and also obtain all the users that signed up for a particular launch. This calls for two methods, `getLaunchIdsByUser`, and `getUsersByLaunch`.
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_src/datasources/user.js_
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```js
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...
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class UserAPI extends DataSource {
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constructor() {
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...
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}
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...
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async getLaunchIdsByUser({ userId }) {
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const found = await this.store.trips.findAll({
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where: { userId: userId },
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});
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return found && found.length
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? found.map(l => l.dataValues.launchId).filter(l => !!l)
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: [];
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}
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async getUsersByLaunch({ launchId }) {
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const found = await this.store.trips.findAll({
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where: { launchId: launchId },
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});
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const userIds = found && found.length ? found.map(l => l.dataValues.userId) : [];
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if (!userIds || !userIds.length) return [];
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const foundUsers = await this.store.users.findAll({
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where: { id: { $in: userIds } },
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});
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if (!foundUsers || !foundUsers.length) return [];
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return foundUsers.map(u => this.userReducer(u));
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}
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}
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...
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```
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Let's analyze the code above.
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In the `getLaunchIdsByUser` method, a `userId` is accepted via the method argument. All the trips booked by a user with a particular `userId` are fetched and stored in the `found` variable. If there are trips found, then an array of launch ids are returned else an empty array is returned.
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In the `getUsersByLaunch` method, a `launchId` is accepted via the method argument. All the trips booked for a particular launch with a specific `launchId` are fetched and stored in the `found` variable. Next, an array of user ids for trips in the `found` variable are obtained and stored in the `userIds` variable. If there are no user ids, then the `userIds` variable becomes an empty array.
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So, if the `userIds` variable is empty, then the `getUsersByLaunch` method returns an empty array. However, if the `userIds` variable is not empty, then users with those ids are fetched from the users table.
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If no users were found, the `getUsersByLaunch` method returns an empty array, else an array of users with their respective `id`, `email` and `avatar` is returned!
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