How do you create a full CRUD GraphQL API for posts in Nest JS?

How do you create a full CRUD GraphQL API for posts in Nest JS?

Sure! I’ll guide you through creating a GraphQL API endpoint for posts in an existing NestJS project. Here are the steps you need to follow:

  1. Install necessary dependencies:

First, ensure you have the necessary GraphQL dependencies installed in your NestJS project. Run the following command in your project directory:

 npm install @nestjs/graphql graphql-tools graphql apollo-server-express
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  1. Set up GraphQL module:

In your app.module.ts, import and configure the GraphQL module:

 import { Module } from '@nestjs/common'; import { GraphQLModule } from '@nestjs/graphql'; import { ApolloDriver, ApolloDriverConfig } from '@nestjs/apollo'; import { join } from 'path'; import { PostsModule } from './posts/posts.module'; // Ensure this path is correct @Module({ imports: [ GraphQLModule.forRoot<ApolloDriverConfig>({ driver: ApolloDriver, autoSchemaFile: join(process.cwd(), 'src/schema.gql'), }), PostsModule, ], }) export class AppModule {}
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  1. Create the Posts module, service, and resolver:

Generate the posts module, service, and resolver using the Nest CLI:

 nest generate module posts nest generate service posts nest generate resolver posts
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  1. Define the Post entity:

Create a post.entity.ts file inside the posts directory with the following content:

 export class Post { id: number; title: string; content: string; }
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  1. Create Post DTOs:

Create create-post.input.ts and update-post.input.ts inside the posts directory:

 // create-post.input.ts import { InputType, Field } from '@nestjs/graphql'; @InputType() export class CreatePostInput { @Field() title: string; @Field() content: string; }
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 // update-post.input.ts import { InputType, Field, Int, PartialType } from '@nestjs/graphql'; @InputType() export class UpdatePostInput extends PartialType(CreatePostInput) { @Field(() => Int) id: number; }
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  1. Update the Post service:

Implement the necessary methods in posts.service.ts:

 import { Injectable } from '@nestjs/common'; import { CreatePostInput } from './dto/create-post.input'; import { UpdatePostInput } from './dto/update-post.input'; import { Post } from './entities/post.entity'; @Injectable() export class PostsService { private posts: Post[] = []; private idCounter = 1; create(createPostInput: CreatePostInput): Post { const newPost = { id: this.idCounter++, ...createPostInput }; this.posts.push(newPost); return newPost; } findAll(): Post[] { return this.posts; } findOne(id: number): Post { return this.posts.find(post => post.id === id); } update(id: number, updatePostInput: UpdatePostInput): Post { const postIndex = this.posts.findIndex(post => post.id === id); if (postIndex === -1) return null; this.posts[postIndex] = { ...this.posts[postIndex], ...updatePostInput }; return this.posts[postIndex]; } remove(id: number): Post { const postIndex = this.posts.findIndex(post => post.id === id); if (postIndex === -1) return null; const removedPost = this.posts.splice(postIndex, 1); return removedPost[0]; } }
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  1. Define the Post resolver:

Implement the resolver in posts.resolver.ts:

 import { Resolver, Query, Mutation, Args, Int } from '@nestjs/graphql'; import { PostsService } from './posts.service'; import { Post } from './entities/post.entity'; import { CreatePostInput } from './dto/create-post.input'; import { UpdatePostInput } from './dto/update-post.input'; @Resolver(of => Post) export class PostsResolver { constructor(private readonly postsService: PostsService) {} @Mutation(() => Post) createPost(@Args('createPostInput') createPostInput: CreatePostInput) { return this.postsService.create(createPostInput); } @Query(() => [Post], { name: 'posts' }) findAll() { return this.postsService.findAll(); } @Query(() => Post, { name: 'post' }) findOne(@Args('id', { type: () => Int }) id: number) { return this.postsService.findOne(id); } @Mutation(() => Post) updatePost(@Args('updatePostInput') updatePostInput: UpdatePostInput) { return this.postsService.update(updatePostInput.id, updatePostInput); } @Mutation(() => Post) removePost(@Args('id', { type: () => Int }) id: number) { return this.postsService.remove(id); } }
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  1. Update the Posts module:

Ensure the posts.module.ts includes the service and resolver:

 import { Module } from '@nestjs/common'; import { PostsService } from './posts.service'; import { PostsResolver } from './posts.resolver'; @Module({ providers: [PostsService, PostsResolver], }) export class PostsModule {}
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  1. Define the GraphQL schema:

Ensure your post.entity.ts is decorated with GraphQL decorators:

 import { ObjectType, Field, Int } from '@nestjs/graphql'; @ObjectType() export class Post { @Field(() => Int) id: number; @Field() title: string; @Field() content: string; }
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Now, you should have a fully functional GraphQL API for managing posts in your NestJS project. You can start your server and access the GraphQL playground at http://localhost:3000/graphql to test your queries and mutations.

Disclaimer: This content is generated by AI.


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