Skip to main content

On GraphQL and building an application using React Apollo

When I visualize building an application, I would think of using React and Redux on the front-end which talks to a set of RESTful services built with Node and Hapi (or Express). However, over a period of time, I've realized that this approach does not scale well when you add new features to the front-end. For example, consider a page that displays user information along with courses that a user has enrolled in. At a later point, you decide to add a section that displays popular book titles that one can view and purchase. If every entity is considered as a microservice then to get data from three different microservices would require three http requests to be sent by the front-end app. The performance of the app would degrade with the increase in the number of http requests.

I read about GraphQL and knew that it is an ideal way of building an app and I need not look forward to anything else. The GraphQL layer can be viewed as a facade which sits on top of your RESTful services or a layer which can be used to talk directly to the persistent layer. This layer provides an interface which allows its clients (front-end apps) to query the required fields from various entities in one single http request.

GraphQL - On the Server

On the server side, GraphQL provides a schema language using which you can construct the domain model. In GraphQL terms, these are `types`, a `type` is used to represent an entity such as User, Course, Book etc. It looks something like this:

type CourseType {
    id: ID!
    name: String
    level: Int
    description: String
}

Here, each field in CourseType entity has a type indicating the value that it can hold (String, Float, Character, Int etc). Apart from the Scalar types, a field could also be used to declare the relationship between two types. For example, a StudentType can have a field `courses` to declare the courses that he/she has enrolled in:

type StudentType {
     id: ID!
     firstName: String
     lastName: String
     courses: [CourseType]!
}

Here the field `courses` is of type `[CourseType]!`. The array notation is used to indicate that a Student record can have a collection of courses i.e. a student can enrol in multiple courses(1-to-many relationship). The bang (!) is used to indicate that it's a required field.

Apart from defining types, one is required to specify what can be retrieved using a `Query` and what can be updated using `Mutation`.

type Query {
    allCourses: [CourseType]
    allStudents: [StudentType]
}

type Mutation {
    createCourse(name: String, level: Int, description: String): CourseType
    createStudent(firstName: String, lastName: String, courses: [CourseType]!): StudentType
    updateCourse(id: ID!, name: String, level: Int, description: String): CourseType
    .
    .
    .
}

Here types `Query` and `Mutation` are special types. They're not used to define an entity, rather they're used to specify the operations that you can perform on these entities. For example, `allCourses` in `Query` is used to declare that the client can use this to retrieve a list of courses (returns [CourseType]). A Mutation type, on the other hand, is used to indicate the operations that you can perform to update these entities. In the above example, createCourse, createStudent etc are the operations that you can perform to add or update records.

All the above types put together come to form the type definition for your schema and it gives a high-level overview of the domain model and the operations that you could perform on various entities. However, the business logic for how the data would be retrieved or updated is not present. To accomplish this, one is required to write resolvers. A resolver provides the implementation that maps to the operations declared in the schema. A sample resolver for the above example looks like this:

const resolvers = {
    Query: {
        allCourses: () => {
            return COURSES;
        }
    },
    Mutation: {
        createCourse: (_, { input }) => {
            let { id, name, description, level } = input;
            COURSES.push({
                id,
                name,
                description,
                level
            });
            return input;
        }
    }
};

The resolvers object contains two properties Query and Mutation; under these, you would define the various operations that can be performed on the entities declared in the schema. Note, that the name of the operations would map to the ones specified in the schema (here allCourses in type Query and createCourse in type Mutation). The type definitions are independent of the language or the platform that you choose. However, the resolvers are written in the language of your choice; in this case JavaScript.

The type definitions and resolvers come together to define the executable schema which can then be used to define middleware in a Node + Express environment:

const schema = makeExecutableSchema({ typeDefs, resolvers});
app.use('/graphql', 
             bodyParser.json(),
             graphqlExpress({
                schema
            }));

I've used `graphql-tools` and `apollo-graphql-express` modules to create the schema and the middleware which would accept incoming requests.

To test the server setup, you could make use of the GraphiQL interface which allows you to inspect the operations declared in the schema, add this:

app.use('/graphiql',
              graphiqlExpress({
                  endpointURL: '/graphql'
              }));

The graphiql interface provides us with a way to test the operations declared in `Query` and `Mutation` of our schema:



Here, the object notation on the left side allows me to specify the query method and the fields that I need from the `courses` model (id and name). The response from the server (on the right side) includes only the data that I have requested. Although the resolver itself returns the entire object, GraphQL ensures that only the requested data is returned in the response; thus reducing the size of the payload.

GraphQL - On the client side

On the client side, the first step would be to connect to the GraphQL server and wrap the root component with the Provider (ApolloProvider from `react-apollo`):

import React from 'react';
import ReactDOM from 'react-dom';
import { ApolloProvider } from 'react-apollo';
import { ApolloClient } from 'apollo-client';
import { HttpLink } from 'apollo-link-http';
import './index.css';
import App from './App';

const client = new ApolloClient({
    link: new HttpLink({ uri: 'http://localhost:8080/graphql' })
})

ReactDOM.render(
    <ApolloProvider client={client}>
        <App />
    </ApolloProvider>, 
    document.getElementById('root'));

Next, we use the `react-apollo` module which provides a higher-order function using which we can glue together a component with the result from a GraphQL query response:

import React, { Component } from 'react';
import { graphql } from 'react-apollo';
import gql from 'graphql-tag';
import Course from './Course';

class CourseList extends Component {
    render() {
        const { allCourses } = this.props.data;
     
        if (!allCourses) return null;
     
        return allCourses.map(course => {
            return (
                <Course key={course.id}
                              course={course} />
            );
        });
    }
}

export default graphql(gql`
    query CourseListQuery {
        allCourses {
            id
            name
            description
        }
    }
`)(CourseList);

Here the graphql higher-order function accepts two arguments - the GraphQL query and the view component that has to be updated with the query result. The result of the query response is passed to the component as props (this.props.data).

Next steps:

I've briefly read about `Relay` and I plan to experiment with it to see how it can be used to connect to a GraphQL server and compare it to see how it fairs with Apollo. 

GitHub repohttps://github.com/sagar-ganatra/react-graphql-apollo-app

Comments

  1. Great material! This is really a good article because you always post grand related content and very informative information with powerful points. Just like the article I was looking for to read the article I found on your website. Thanks for sharing this piece of writing on this website. I want to tell you that it is very helpful for us. Thanks for sharing such an awesome blog with us. I want to visit again.

    ReplyDelete
  2. The main purpose of education is to help students gain the knowledge and skills so that they will be able to function in society. Students need to be provided with the necessary skills so that they can learn to become productive citizens. There are many advantages that are associated with receiving an education. Students will be able to contribute to their community and help make it a better place to live. Education basically helps shape society because it helps students learn to become more sociable and helps them develop relationships with their peers. Students will be more qualified for different job positions if they have a good solid education. Education is vital to each student’s life, therefore, by working hard to provide the best instruction possible will help train students to become future leaders and will lead to a better life.
    Education is essential to every student’s life as well as their future. Students can have a prosperous life by receiving a good quality education. My thoughts are that students need to learn from the books along with other various materials just as I did while growing up. The classroom curriculum should be decided by their teacher and the teacher should set clear goals as to what is expected from the students. Students should work hard to achieve their goals because it will certainly be worth it in the end. According to essentialism, ‘Schools should not radically try to reshape society but schools should transmit traditional moral values and intellectual knowledge that students need to become model citizens’. Read about education help at School Uniforms benefits . The school should stress the importance of values because some children are not taught these at home. Teaching children good values helps build their character and helps them become respectable people. In regards to education, I think society is important because this is a place where we all live so we should work to make it a better place.

    ReplyDelete
  3. I work and study at the same time, so I originally planned to write my dissertation myself. Family, children, work, so there is simply no time for this. I learned that it is possible to order the writing of deserting to order - Paperhelpers service. Of course, I was worried whether everything will be fine, but it turned out that the authors work professionally and efficiently.

    ReplyDelete
  4. The information you have provided would be a great addition to unemployed professors review . So thank you

    ReplyDelete
  5. Crypto-currency as a modern form of the digital asset has received a worldwide acclaim for easy and faster financial transactions and its awareness among people have allowed them to take more interest in the field thus opening up new and advanced ways of making payments. Crypto.com Referral Code with the growing demand of this global phenomenon more,new traders and business owners are now willing to invest in this currency platform despite its fluctuating prices however it is quite difficult to choose the best one when the market is full. In the list of crypto-currencies bit-coins is one of the oldest and more popular Crypto.com Referral Code for the last few years. It is basically used for trading goods and services and has become the part of the so-called computerized block-chain system allowing anyone to use it thus increasing the craze among the public, Crypto.com Referral Code.

    Common people who are willing to purchase BTC can use an online wallet system for buying them safely in exchange of cash or credit cards and in a comfortable way from the thousands of BTC foundations around the world and keep them as assets for the future. Due to its popularity, many corporate investors are now accepting them as cross-border payments and the rise is unstoppable. With the advent of the internet and mobile devices,information gathering has become quite easy as a result the BTC financial transactions are accessible and its price is set in accordance with people’s choice and preferences thus leading to a profitable investment with Crypto.com Referral Code Code. Recent surveys have also proved that instability is good for BTC exchange as if there is instability and political unrest in the country due to which banks suffer then investing in BTC can surely be a better option. Again bit-coin transaction fees are pretty cheaper and a more convenient technology for making contracts thus attracting the crowd. The BTC can also be converted into different fiat currencies and is used for trading of securities, for land titles, document stamping, public rewards and vice versa.

    Another advanced block-chain project is Ethereumor the ETH which has served much more than just a digital form of crypto-currency Crypto.com Referral Code and its popularity in the last few decades have allowed billions of people to hold wallets for them. With the ease of the online world,the ETH have allowed the retailers and business organizations to accept them for trading purposes, therefore, can serve as the future of the financial system.

    ReplyDelete
  6. Our full Lace Front Wigs are all hand made with a lace cap. They are manufactured with thin lace sewn on top of the cap. Individual hairs are then sewn onto the thin lace. Each lace wig has lace all around the unit which will need to be cut prior to securing the wig to your head. You will need to cut along the hairline around your entire head. By doing so, you will be able to wear your hair anyway you like. You can even style ponytails, up-dos, etc. Once the Lace Wigs is successfully applied, it will appear that all the hair is growing directly from your head!

    Lace front wigs are hand-made with lace front cap & machine weft at back. Lace front wigs are manufactured with a thin lace that extends from ear to ear across the hairline. When you receive the wig, the lace will be quite long in the front. Cut and style according to your preference, as you will need to apply adhesive along the front of the wig. Once the wig is applied, you will still have Lace Wigs with a very natural appearance.
    TeamWigz Provide the Best Lace Front Wigs and Lace Wigs in Johannesburg and South Africa.

    ReplyDelete
  7. 우리카지노 에 오신 것을 환영합니다. 국내 최고의 카지노사이트 에 가입하여 바카라사이트 에서 다양한 게임을 즐기시면서 대박의 기회를 놓치지마세요! 우리 카지노는 한국의 바카라 산업을 지배하는 카지노 사이트입니다. 우리 카지노는 한국 바카라 시장 점유율의 50 % 이상을 차지하는 10 년 이상 온라인 바카라 시장을 지배 해 왔기 때문에 우리 카지노를 모르는 사람은 거의 없습니다.

    ARTICLE: 우리카지노는 대한민국의 바카라 업계를 장악하고 있는 카지노사이트 입니다. 우리카지노가 대한 민국에서 장악한 바카라 시장점유율이 50%가 넘고 10년 넘게 온라인 바카라 시장을 장악해왔기 때문에 대한민국에서는 우리카지노를 모르는 사람은 드뭅니다. 이런 바카라 업계의 독보적인 입지 때문에 늘 유명하거나 최고만을 찾는 사람들이 카지노사이트를 찾을때는 늘 우리카지노를 찾습니다.바카라를 처음 시작하시는 초보자분들에게도 우리카지노에서 카지노사이트를 시작하시기 좋은 환경입니다. 우리카지노사이트에서는 신규가입시 3만쿠폰을 지급 해주기 때문입니다. 사람들이 늘 1등만을 찾는 이유는 분명 있습니다. 다른 카지노사이트와는 달리 우리카지노를 이용하실시 에이전트를 끼고 게임을 하신다면 본사 이외에 활동쿠폰 및 오링쿠폰을 별도로 제공해주고 있기 때문입니다. 이러한 이유들 때문에 카지노사이트 업계에서 바카라를 즐기신다면 다들 우리카지노를 선호 하십니다. 카지노사이트에서 바카라를 이기기 물론 어렵습니다. 하지만 우리카지노의 에이전트를 끼고 바카라를 즐기신다면 승산이 있다고 봅니다. 우리카지노 에이전트의 연락처는 홈페이지로 연락하시면 언제든지 부담없이 소통가능 합니다. 카지노사이트를 선정할때는 바카라를 다른곳보다 유리하게 즐길 수 있는 카지노를 선택해야한다고 생각합니다. 그것이 바로 우리카지노 입니다. 이상으로 우리카지노와 바카라 카지노사이트 사이의 상관관계를 알아보았습니다바카라사이트.

    ReplyDelete
  8. Thanks a lot for a great article. I was hooked on reading it. In case you wanna check similar articles, go to service on https://topwritingservice.com/white-paper-writer/. Hope you'll like it a lot. There are loads of intersting posts.

    ReplyDelete

Post a Comment

Popular posts from this blog

De-obfuscating javascript code in Chrome Developer Tools

I had blogged about JavaScript debugging with Chrome Developer Tools some time back, wherein I have explained how these developer tools can help in debugging javascript code. Today Google Chrome 12 was released and my Chrome browser was updated to this version. As with every release, there have been some improvements made on performance, usability etc,. One feature that stood out for me is the ability to De-obfuscate the javascript code.

What is Minification?

Minification is the process of removing unnecessary characters such as white spaces, comments, new lines from the source code. These otherwise would be added to make the code more readable. Minifying the source code helps in reducing the file size and thereby reducing the time taken to download the file. This is the reason why most of the popular javascript libraries such as jQuery are minified. A minified jQuery file is of 31 KB in size where as an uncompressed one is about 229 KB. Unfortunately, debugging minified javascript file…

Adding beforeRender and afterRender functions to a Backbone View

I was working on a Backbone application that updated the DOM when a response was received from the server. In a Backbone View, the initialize method would perform some operations and then call the render method to update the view. This worked fine, however there was scenario where in I wanted to perform some tasks before and after rendering the view. This can be considered as firing an event before and after the function had completed its execution. I found a very simple way to do this with Underscore's wrap method.

Custom validation messages for HTML5 Input elements using the constraint validation API

HTML5 has introduced several input types such as EMAIL, URL, RANGE, SEARCH, DATE, TIME, etc,. Most of the modern browsers have implemented them and are ready to be used in a HTML document. Another exciting feature introduced in HTML5 is the form validation. Instead of writing JavaScript to validate users input, browsers can now validate it and show an appropriate message if the validation fails. The validation message is shown in line with the field for which the validation has failed. The default error message is shown when the validation fails. In this post I'll explain how these error messages can be changed.