Graph QL

Problems with REST API

GET id -------------------> data GET id2 -------------------> more data

GET data.id ------------------> even more data

Multiple Round Trips● In order to descent into the object graph, multiple

round trips to the server are required.

● Critical for Mobile Environment

Over fetchingUnless specifically designed, you might receive needless information

Compatibility and Versioning

http://api.myservice.com/v1/usershttp://api.myservice.com/v2/usershttp://api.myservice.com/v3/users

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Backend APIs are storage-centric

Front-end APIs are product-centric

Graph Application Layer Query Language (not Storage Query Language)

“A better solution that can replace restful server and mvc framework”

Basically JSON without the values

No custom endpoints

Clients ask exactly what they want

person:{ name:, address: }

Graph QL

● User-defined type system - “schema”

● Server describes what data is available

● Clients describe what data they require

● User-defined data fetching (“how do I get an article”)

● Front end request independent to backend

How Graph QL Works

GraphQL has a type system

Three main “types” required to get an endpoint up and running.

1. A type for the model2. A type for the query3. A type for the schema

In reality, it is more complex than this.(forget about it for now)

Our Data

var goldbergs = { 1: { character: "Beverly Goldberg", actor: "Wendi McLendon-Covey", role: "matriarch", traits: "embarrassing, overprotective", id: 1 }, 2: { character: "Murray Goldberg", actor: "Jeff Garlin", role: "patriarch", traits: "gruff, lazy", id: 2 }, 3: { character: "Erica Goldberg", actor: "Hayley Orrantia", role: "oldest child", traits: "rebellious, nonchalant", id: 3 }, 4: { character: "Barry Goldberg", actor: "Troy Gentile", role: "middle child", traits: "dim-witted, untalented", id: 4 }, 5: { character: "Adam Goldberg", actor: "Sean Giambrone", role: "youngest child", traits: "geeky, pop-culture obsessed", id: 5 }, 6: { character: "Albert 'Pops' Solomon", actor: "George Segal", role: "grandfather", traits: "goofy, laid back", id: 6 }}

Model TypeModel Type is pretty much a mirror image of each Goldberg in our goldbergs data --------->

var goldbergType = new GraphQLObjectType({ name: "Goldberg", description: "Member of The Goldbergs", fields: { character: { type: GraphQLString, description: "Name of the character", }, actor: { type: GraphQLString, description: "Actor playing the character", }, role: { type: GraphQLString, description: "Family role" }, traits: { type: GraphQLString, description: "Traits this Goldberg is known for" }, id: { type: GraphQLInt, description: "ID of this Goldberg" } }});

1. Create a new instance of GraphQLObjectType, “Goldberg”

2. Under “fields”: Each “type” indicates the type expected (e.g. string (GraphQLString) for character, int (GraphInt) for id.)

3. “description” fields are good for self-documentation

Query TypeThe query type tells how we will query our data

var queryType = new GraphQLObjectType({ name: "query", description: "Goldberg query", fields: { goldberg: { type: goldbergType, args: { id: { type: GraphQLInt } }, resolve: function(_, args){ return getGoldberg(args.id) } } }});

function getGoldberg(id) { return goldbergs[id]}

1. Query Type is an instance of GraphQLObjectType, it just serves a different purpose.

2. Create a new query field called goldberg and set its “type” to the goldbergType we created earlier. Our new goldberg field will accept an id as an assignment.

3. When we resolve our query we return the output of a function getGoldberg()

Schema TypeSchema type combines them all together.

/* creating schema instance */

var schema = new GraphQLSchema({ query: queryType});

/* serve our schema */

var graphQLServer = express();graphQLServer.use('/', graphqlHTTP({ schema: schema, graphiql: true }));graphQLServer.listen(8080);console.log("The GraphQL Server is running.")

{ goldberg ( id : 2 ) { id, character }}

{ “data” : { “goldberg” : { “id” : 2, “character” : “Murray Goldberg” }}

Let’s Test

Go to GraphiQL IDE and test it yourself. (GraphiQL IDE is just like postman of RESTful API for GraphQL)

React and Redux

Let’s delete the “hello world” from static/index.html and add a new message using React in index.js:

| -- app | -- actions | -- components | -- reducers

In the “reducers” folder we’ll create a new file called reducer.js where we’ll work on our reducer function.

import React from "react";import ReactDOM from "react-dom";const Main = React.createClass({ render: () => { return ( <div> <p>hello react!</p> </div> ) }});ReactDOM.render( <Main />, document.getElementById("example"));

React and Redux

We’ll be using the Immutable module for our state so that we can form some good habits.

Our state has two fields — one to let us know if we are in the middle of a query/awaiting a response from the server and another that contains the response data.

Next we plug our immutableState into a reducer function:

import Immutable from "immutable";const immutableState = Immutable.Map({ fetching: false, data: Immutable.Map({})})

--------------------------------------------------

export const queryReducer = (state = immutableState, action) => { switch (action.type) { case "STARTING_REQUEST": return state.set("fetching", true); case "FINISHED_REQUEST": return state.set("fetching", false) .set("data", Immutable.Map(action.response.data.goldberg)); default: return state }}

StoreBack in index.js we want to create a store out of our reducer and feed it to our main component.

We’ll need to import the reducer we just created along with some helpers from redux and react-redux.

We also need the redux-thunk middleware to help us later on when we need to make some requests.

import React from "react";import ReactDOM from "react-dom";import { createStore, applyMiddleware } from "redux";import { Provider } from "react-redux";import { queryReducer } from "./app/reducers/reducers.js";import thunkMiddleware from "redux-thunk";

/* First, we apply the redux-thunk middleware:*/const createStoreWithMiddleware = applyMiddleware( thunkMiddleware)(createStore)

/* Then we wrap our Main component in the Redux Provider and pass our queryReducer into createStoreWithMiddleware.*/

ReactDOM.render( <Provider store={createStoreWithMiddleware(queryReducer)}> <Main /> </Provider>, document.getElementById("example"));

ActionsIn the “actions” folder we’ll create a new file called actions.js.

We need to create two actions to dispatch to our reducer,

one for “STARTING_REQUEST”

and one for “FINISHED_REQUEST”:

const startingRequest = () => { return { type: "STARTING_REQUEST" }}const finishedRequest = (response) => { return { type: "FINISHED_REQUEST", response: response }}

ActionsThe great thing about the redux-thunk middleware we applied to our store earlier is that when an action returns a function that function is injected with dispatch().

We’ll get to use dispatch() twice in a new action called getGraph:

When getGraph() is called we dispatch startingRequest() to indicate the start of a new query. We then begin the async request (note the “application/graphql” content type in the header) and when our query is complete we dispatch finishedRequest() with the results of our query.

export const getGraph = (payload) => { return dispatch => { dispatch(startingRequest()); return new Promise(function(resolve, reject) { let request=new XMLHttpRequest(); request.open("POST", "/graphql", true); request.setRequestHeader("Content-Type", "application/graphql"); request.send(payload); request.onreadystatechange = () => { if (request.readyState === 4) { resolve(request.responseText) } } }).then(response => dispatch(finishedRequest(JSON.parse(response)))) }}

ComponentFor now we’ll create an empty Query component:

We need to hook up our component with our store and the dispatch method by creating a container component and using the react-redux connect() helper.

import React from ‘react’;import { connect } from ‘react-redux’;import { getGraph } from ‘../actions/actions.js’;

let Query = React.createClass({ render() { return ( <div> </div> ) }});

const mapStateToProps = (state) => { return { store: state }};export const QueryContainer = connect( mapStateToProps)(Query);

let Query = React.createClass({ componentDidMount() { this.props.dispatch( getGraph("{goldberg(id: 2) {id, character, actor}}") ); }});

ComponentWe’ll also add the elements that our response data will fill and a button to submit additional queries. We want to know if we are in the middle of a query so we’ll grab our fetching field from our state and display it on the page.

let Query = React.createClass({ componentDidMount() { this.props.dispatch( getGraph("{goldberg(id: 2) {id, character, actor}}") ); }, render() { let dispatch = this.props.dispatch; let fetchInProgress = String(this.props.store.get('fetching')); let queryText; let goldberg = this.props.store.get('data').toObject(); return ( <div> <p>Fetch in progress: {fetchInProgress}</p> <h3>{ goldberg.character }</h3> <p>{ goldberg.actor }</p> <p>{ goldberg.role }</p> <p>{ goldberg.traits }</p> <input ref={node => {queryText = node}}></input> <button onClick={() => { dispatch(getGraph(queryText.value))} }> query </button> </div> ) }});

ComponentWith that done, the last thing we have to do is plug our QueryContainer component into our Main component.In index.js:

import { QueryContainer } from “./app/components/Query.js”;

// And replace “hello react!”const Main = () => { return ( <div> <QueryContainer /> </div> )};

● https://learngraphql.com/basics/introduction● https://medium.com/@thisbejim/getting-started-with-redux-and-graphql-83

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Resources used in this Presentation

Go to GraphiQL IDE and test it yourself. (GraphiQL IDE is just like postman of RESTful API for GraphQL)