Iesācēja GraphQL ceļvedis

Viens no mūsdienās visbiežāk apspriestajiem terminiem ir API. Daudzi cilvēki precīzi nezina, kas ir API. Būtībā API apzīmē lietojumprogrammu saskarni. Tā, kā teikts nosaukumā, ir saskarne, ar kuru cilvēki - izstrādātāji, lietotāji, patērētāji - var mijiedarboties ar datiem.

Jūs varat domāt par API kā bārmeni. Jūs prasāt bārmenim dzērienu, un viņi dod jums to, ko jūs gribējāt. Vienkārši. Tad kāpēc tā ir problēma?

Kopš mūsdienu tīmekļa sākuma API veidošana nav bijusi tik grūta, kā izklausās. Bet API mācīšanās un izpratne bija. Izstrādātāji veido lielāko daļu cilvēku, kuri izmantos jūsu API, lai kaut ko izveidotu vai vienkārši patērētu datus. Tātad jūsu API jābūt pēc iespējas tīrākam un intuitīvākam. Labi izstrādātu API ir ļoti viegli izmantot un iemācīties. Tas ir arī intuitīvs, labs punkts, kas jāpatur prātā, kad sākat izstrādāt savu API.

Mēs jau ilgu laiku izmantojām REST, lai izveidotu API. Kopā ar to rodas dažas problēmas. Veidojot API, izmantojot REST dizainu, jūs saskaras ar dažām problēmām, piemēram:

1) jums būs daudz galapunktu

2) izstrādātājiem būs daudz grūtāk iemācīties un saprast jūsu API

3) notiek pārāk liela un nepietiekama informācijas iegūšana

Lai atrisinātu šīs problēmas, Facebook izveidoja GraphQL. Šodien es domāju, ka GraphQL ir labākais veids, kā izveidot API. Šis raksts jums pateiks, kāpēc jums tas jāsāk mācīties jau šodien.

Šajā rakstā jūs uzzināsiet, kā darbojas GraphQL. Es jums parādīšu, kā izveidot ļoti labi izstrādātu, efektīvu, jaudīgu API, izmantojot GraphQL.

Jūs, iespējams, jau esat dzirdējuši par GraphQL, jo daudzi cilvēki un uzņēmumi to izmanto. Kopš GraphQL ir atvērtā koda, tā kopiena ir kļuvusi milzīga.

Ir pienācis laiks sākt praksē uzzināt, kā darbojas GraphQL, un visu par tā burvību.

Kas ir GraphQL?

GraphQL ir atvērtā koda vaicājumu valoda, kuru izstrādājusi Facebook. Tas mums nodrošina efektīvāku mūsu API izstrādi, izveidi un patēriņu. Būtībā tas ir REST aizstājējs.

GraphQL ir daudz funkciju, piemēram:

  1. Jūs rakstāt vēlamos datus un iegūstat tieši tos datus, kurus vēlaties. Vairs nevajadzēs pārmērīgi iegūt informāciju, kā mēs esam pieraduši pie REST.
  2. Tas dod mums vienu galapunktu , tai pašai API vairs nav 2. vai 3. versijas.
  3. GraphQL ir stingri ierakstīts , un līdz ar to pirms izpildes jūs varat validēt vaicājumu GraphQL tipa sistēmā. Tas palīdz mums izveidot jaudīgākas API.

Šis ir pamatinformācija par GraphQL - kāpēc tā ir tik spēcīga un kāpēc mūsdienās tā iegūst lielu popularitāti. Ja vēlaties uzzināt vairāk par to, iesaku jums apmeklēt GraphQL vietni un to pārbaudīt.

Darba sākšana

Šī raksta galvenais mērķis nav iemācīties iestatīt GraphQL serveri, tāpēc pagaidām mēs to neiedziļināmies. Mērķis ir uzzināt, kā GraphQL darbojas praksē, tāpēc mēs izmantosim nulles konfigurācijas GraphQL serveri ar nosaukumu Graphpack.

Lai sāktu mūsu projektu, mēs izveidosim jaunu mapi, un jūs to varat nosaukt kā vien vēlaties. Es to nosaukšu graphql-server:

Atveriet termināli un ierakstiet:

mkdir graphql-server

Tagad jūsu mašīnā vajadzētu būt instalētai npm vai dzijai . Ja nezināt, kas tie ir, npm un dzija ir JavaScript programmēšanas valodas pakotņu pārvaldnieki. Vietnei Node.js noklusējuma pakotņu pārvaldnieks ir npm .

Izveidotās mapes iekšpusē ierakstiet šādu komandu:

npm init -y

Vai arī, ja izmantojat dziju:

yarn init 

npm izveidos package.jsonjums failu, un visas instalētās atkarības un jūsu komandas būs tur.

Tātad tagad mēs instalēsim vienīgo atkarību, kuru izmantosim.

☄️Graphpack ļauj jums izveidot GraphQL serveri ar nulles konfigurāciju . Tā kā mēs tikko sākam darbu ar GraphQL, tas mums ļoti palīdzēs turpināt un uzzināt vairāk, neuztraucoties par servera konfigurāciju.

Termināla saknes mapē instalējiet to šādi:

npm install --save-dev graphpack

Vai arī, ja izmantojat dziju, jums vajadzētu rīkoties šādi:

yarn add --dev graphpack

Kad Graphpack ir instalēts, dodieties uz mūsu skriptiem package.jsonfailā un ievietojiet tur šādu kodu:

"scripts": { "dev": "graphpack", "build": "graphpack build" }

Mēs izveidosim mapi ar nosaukumu src, un tā būs vienīgā mape visā mūsu serverī.

Izveidojiet mapi ar nosaukumu src, pēc tam mapē mēs izveidosim tikai trīs failus.

Mūsu srcmapē izveidojiet failu ar nosaukumu schema.graphql. Pirmajā failā ievietojiet šādu kodu:

type Query { hello: String }

Šajā schema.graphqlfailā būs visa mūsu GraphQL shēma. Ja jūs nezināt, kas tas ir, es paskaidrošu vēlāk - neuztraucieties.

Tagad srcmapē izveidojiet otru failu. Zvaniet tam resolvers.jsun šajā otrajā failā ievietojiet šādu kodu:

import { users } from "./db"; const resolvers = { Query: { hello: () => "Hello World!" } }; export default resolvers;

Šis resolvers.jsfails būs veids, kā mēs sniegsim instrukcijas, kā GraphQL darbību pārveidot par datiem.

Visbeidzot, srcmapē izveidojiet trešo failu. Zvaniet tam db.jsun šajā trešajā failā ievietojiet šādu kodu:

export let users = [ { id: 1, name: "John Doe", email: "[email protected]", age: 22 }, { id: 2, name: "Jane Doe", email: "[email protected]", age: 23 } ];

In this tutorial we’re not using a real-world database. So this db.js file is going to simulate a database, just for learning purposes.

Now our src folder should look like this:

src |--db.js |--resolvers.js |--schema.graphql

Now, if you run the command npm run dev or, if you’re using yarn, yarn dev, you should see this output in your terminal:

You can now go to localhost:4000 . This means that we’re ready to go and start writing our first queries, mutations, and subscriptions in GraphQL.

You see the GraphQL Playground, a powerful GraphQL IDE for better development workflows. If you want to learn more about GraphQL Playground, click here.

Schema

GraphQL has its own type of language that’s used to write schemas. This is a human-readable schema syntax called Schema Definition Language (SDL). The SDL will be the same, no matter what technology you’re using — you can use this with any language or framework that you want.

This schema language its very helpful because it’s simple to understand what types your API is going to have. You can understand it just by looking right it.

Types

Types are one of the most important features of GraphQL. Types are custom objects that represent how your API is going to look. For example, if you’re building a social media application, your API should have types such as Posts, Users, Likes, Groups.

Types have fields, and these fields return a specific type of data. For example, we’re going to create a User type, we should have some name, email, and age fields. Type fields can be anything, and always return a type of data as Int, Float, String, Boolean, ID, a List of Object Types, or Custom Objects Types.

So now to write our first Type, go to your schema.graphql file and replace the type Query that is already there with the following:

type User { id: ID! name: String! email: String! age: Int }

Each User is going to have an ID, so we gave it an ID type. User is also going to have a name and email, so we gave it a String type, and an age, which we gave an Int type. Pretty simple, right?

But, what about those ! at the end of every line? The exclamation point means that the fields are non-nullable, which means that every field must return some data in each query. The only nullable field that we’re going to have in our User type will be age.

In GraphQL, you will deal with three main concepts:

  1. queries — the way you’re going to get data from the server.
  2. mutations — the way you’re going to modify data on the server and get updated data back (create, update, delete).
  3. subscriptions — the way you’re going to maintain a real-time connection with the server.

I’m going to explain all of them to you. Let’s start with Queries.

Queries

To explain this in a simple way, queries in GraphQL are how you’re going to get data. One of the most beautiful things about queries in GraphQL is that you are just going to get the exact data that you want. No more, no less. This has a huge positive impact in our API — no more over-fetching or under-fetching information as we had with REST APIs.

We’re going to create our first type Query in GraphQL. All our queries will end up inside this type. So to start, we’ll go to our schema.graphql and write a new type called Query:

type Query { users: [User!]! }

It’s very simple: the usersquery will return to us an array of one or more Users. It will not return null, because we put in the ! , which means it’s a non-nullable query. It should always return something.

But we could also return a specific user. For that we’re going to create a new query called user. Inside our Query type, put the following code:

user(id: ID!): User! 

Now our Query type should look like this:

type Query { users: [User!]! user(id: ID!): User! }

As you see, with queries in GraphQL we can also pass arguments. In this case, to query for a specific user, we’re going to pass its ID.

But, you may be wondering: how does GraphQL know where get the data? That’s why we should have a resolvers.js file. That file tells GraphQL how and where it's going to fetch the data.

First, go to our resolvers.js file and import the db.js that we just created a few moments ago. Your resolvers.js file should look like this:

import { users } from "./db"; const resolvers = { Query: { hello: () => "Hello World!" } }; export default resolvers;

Now, we’re going to create our first Query. Go to your resolvers.js file and replace the hello function. Now your Query type should look like this:

import { users } from "./db"; const resolvers = { Query: { user: (parent, { id }, context, info) => { return users.find(user => user.id === id); }, users: (parent, args, context, info) => { return users; } } }; export default resolvers;

Now, to explain how is it going to work:

Each query resolver has four arguments. In the user function, we’re going to pass id as an argument, and then return the specific user that matches the passed id. Pretty simple.

In the users function, we’re just going to return the users array that already exists. It’ll always return to us all of our users.

Now, we’re going to test if our queries are working fine. Go to localhost:4000 and put in the following code:

query { users { id name email age } }

It should return to you all of our users.

Or, if you want to return a specific user:

query { user(id: 1) { id name email age } }

Now, we’re going to start learning about mutations, one of the most important features in GraphQL.

Mutations

In GraphQL, mutations are the way you’re going to modify data on the server and get updated data back. You can think like the CUD (Create, Update, Delete) of REST.

We’re going to create our first type mutation in GraphQL, and all our mutations will end up inside this type. So, to start, go to our schema.graphql and write a new type called mutation:

type Mutation { createUser(id: ID!, name: String!, email: String!, age: Int): User! updateUser(id: ID!, name: String, email: String, age: Int): User! deleteUser(id: ID!): User! }

As you can see, we’re going to have three mutations:

createUser: we should pass an ID, name, email, and age. It should return a new user to us.

updateUser: we should pass an ID, and a new name, email, or age. It should return a new user to us.

deleteUser: we should pass an ID. It should return a new user to us.

Now, go to our resolvers.js file and below the Query object, create a new mutation object like this:

Mutation: { createUser: (parent, { id, name, email, age }, context, info) => { const newUser = { id, name, email, age }; users.push(newUser); return newUser; }, updateUser: (parent, { id, name, email, age }, context, info) => { let newUser = users.find(user => user.id === id); newUser.name = name; newUser.email = email; newUser.age = age; return newUser; }, deleteUser: (parent, { id }, context, info) => { const userIndex = users.findIndex(user => user.id === id); if (userIndex === -1) throw new Error("User not found."); const deletedUsers = users.splice(userIndex, 1); return deletedUsers[0]; } }

Now, our resolvers.js file should look like this:

import { users } from "./db"; const resolvers = { Query: { user: (parent, { id }, context, info) => { return users.find(user => user.id === id); }, users: (parent, args, context, info) => { return users; } }, Mutation: { createUser: (parent, { id, name, email, age }, context, info) => { const newUser = { id, name, email, age }; users.push(newUser); return newUser; }, updateUser: (parent, { id, name, email, age }, context, info) => { let newUser = users.find(user => user.id === id); newUser.name = name; newUser.email = email; newUser.age = age; return newUser; }, deleteUser: (parent, { id }, context, info) => { const userIndex = users.findIndex(user => user.id === id); if (userIndex === -1) throw new Error("User not found."); const deletedUsers = users.splice(userIndex, 1); return deletedUsers[0]; } } }; export default resolvers;

Now, we’re going to test if our mutations are working fine. Go to localhost:4000 and put in the following code:

mutation { createUser(id: 3, name: "Robert", email: "[email protected]", age: 21) { id name email age } }

It should return a new user to you. If you want to try making new mutations, I recommend you to try for yourself! Try to delete this same user that you created to see if it’s working fine.

Finally, we’re going to start learning about subscriptions, and why they are so powerful.

Subscriptions

As I said before, subscriptions are the way you’re going to maintain a real-time connection with a server. That means that whenever an event occurs in the server and whenever that event is called, the server will send the corresponding data to the client.

By working with subscriptions, you can keep your app updated to the latest changes between different users.

A basic subscription is like this:

subscription { users { id name email age } }

You will say it’s very similar to a query, and yes it is. But it works differently.

When something is updated in the server, the server will run the GraphQL query specified in the subscription, and send a newly updated result to the client.

We’re not going to work with subscriptions in this specific article, but if you want to read more about them click here.

Conclusion

Kā redzējāt, GraphQL ir jauna tehnoloģija, kas ir patiešām spēcīga. Tas dod mums reālu spēku veidot labākus un labi izstrādātus API. Tāpēc iesaku to sākt mācīties jau tagad. Man tas galu galā aizstās REST.

Paldies, ka izlasījāt rakstu.

Seko man Twitter!

Seko man GitHub!

Es meklēju attālinātu iespēju, tāpēc, ja ir kādi, es labprāt par to uzzinātu, tāpēc, lūdzu, sazinieties ar mani savā Twitter vietnē !