GraphQL CRUD

1. Setting Up a GraphQL Server

Install Required Packages

Using Node.js, install the necessary GraphQL packages:

bash

npm install graphql express express-graphql

Basic GraphQL Server Setup

const express = require('express');
const { graphqlHTTP } = require('express-graphql');
const { buildSchema } = require('graphql');

// Define schema
const schema = buildSchema(`
  type User {
    id: ID!
    name: String!
    email: String!
  }

  input UserInput {
    name: String!
    email: String!
  }

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

  type Mutation {
    createUser(input: UserInput): User
    updateUser(id: ID!, input: UserInput): User
    deleteUser(id: ID!): User
  }
`);

// Sample data
const users = [];

// Define resolvers
const root = {
  users: () => users,
  user: ({ id }) => users.find(user => user.id === id),
  createUser: ({ input }) => {
    const newUser = { id: String(users.length + 1), ...input };
    users.push(newUser);
    return newUser;
  },
  updateUser: ({ id, input }) => {
    const userIndex = users.findIndex(user => user.id === id);
    if (userIndex > -1) {
      users[userIndex] = { id, ...input };
      return users[userIndex];
    }
    throw new Error('User not found');
  },
  deleteUser: ({ id }) => {
    const userIndex = users.findIndex(user => user.id === id);
    if (userIndex > -1) {
      const deletedUser = users.splice(userIndex, 1)[0];
      return deletedUser;
    }
    throw new Error('User not found');
  },
};

// Start server
const app = express();
app.use(
  '/graphql',
  graphqlHTTP({
    schema,
    rootValue: root,
    graphiql: true,
  })
);

app.listen(4000, () => {
  console.log('GraphQL API running at http://localhost:4000/graphql');
});

2. CRUD Operations with GraphQL

Create (POST)

In GraphQL, creating data involves using a mutation to add new entries.

Example: Mutation

mutation {
  createUser(input: { name: "John Doe", email: "john.doe@example.com" }) {
    id
    name
    email
  }
}

Response

{
  "data": {
    "createUser": {
      "id": "1",
      "name": "John Doe",
      "email": "john.doe@example.com"
    }
  }
}

Read (GET)

The Read operation retrieves data using a query. Clients can specify the fields within the CRUD app they want.

Example: Query (All Users)

query {
  users {
    id
    name
    email
  }
}

Response

{
  "data": {
    "users": [
      { "id": "1", "name": "John Doe", "email": "john.doe@example.com" }
    ]
  }
}

Example: Query (Single User)

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

Response

{
  "data": {
    "user": { "id": "1", "name": "John Doe", "email": "john.doe@example.com" }
  }
}

Update (PUT/PATCH)

Updating data in GraphQL involves using a mutation to modify existing entries.

Example: Mutation

mutation {
  updateUser(id: "1", input: { name: "John Updated", email: "john.updated@example.com" }) {
    id
    name
    email
  }
}

Response

{
  "data": {
    "updateUser": {
      "id": "1",
      "name": "John Updated",
      "email": "john.updated@example.com"
    }
  }
}

Delete (DELETE)

Deleting data involves using a mutation to remove an entry by ID.

Example: Mutation

mutation {
  deleteUser(id: "1") {
    id
    name
    email
  }
}

Response

{
  "data": {
    "deleteUser": {
      "id": "1",
      "name": "John Doe",
      "email": "john.doe@example.com"
    }
  }
}

Notable libraries and example projects

1. NestJS Query - Library for building CRUD APIs with NestJS and GraphQL
2. NestJS GraphQL Best Practice - Best practice example for building a CRUD API using NestJS and GraphQL