GraphQL 实践篇一

PatWu16

Nestjs+GraphQL搭建服务

前面我们介绍了GraphQL的概念和基础知识,这篇文章记录下使用Nestjs+GraphQL搭建Node服务。

安装

npm i --save @nestjs/graphql graphql-tools graphql apollo-server-express

注册

// app.module.ts
import { Module } from '@nestjs/common';
import { GraphQLModule } from '@nestjs/graphql';
import { ConfigModule, ConfigService } from 'nestjs-config';
@Module({
 imports: [
    ConfigModule.load(path.resolve(__dirname, 'config', '**/!(*.d).{ts,js}')),
    GraphQLModule.forRootAsync({
        imports: [ConfigModule],
        useFactory: (config: ConfigService) => config.get('graphql'),
        inject: [ConfigService],
    }) 
 ],})
export class ApplicationModule {}

// src/config/graphql.ts
import * as path from 'path';
export default {
  autoSchemaFile: path.join(process.cwd(), 'src/schema.gql'), // 最后生成的`Schema 文件,不可修改`
  installSubscriptionHandlers: true, // 启用订阅
};

启动项目,并访问 http://localhost:3000/graphql,我们便可以看到graphql页面。
image

编写服务端逻辑

接下来我们注册一个author模块,目录结构如下:
image.png

// author.module.ts
import { Module } from '@nestjs/common';
import { AuthorService } from './author.service';
import { AuthorResolver } from './author.resolver';
@Module({
  providers: [
    AuthorService, 
    AuthorResolver
  ]
})
export class AuthorModule {}
// author.service.ts
// 此文件用于写数据库查询等逻辑,我们着重学习GraphQL的使用,故此处不做相关Demo
import { Injectable } from '@nestjs/common';
@Injectable()
export class AuthorService {
  async findOneById() {}
}
// author.resolver.ts
import { Args, Mutation, Query, Resolver, Subscription, ResolveField, Parent, Int } from '@nestjs/graphql';
import { PubSub } from 'graphql-subscriptions';
import { Author } from './models/author.model';
import { Post } from './models/post.model';
import { AuthorService } from './author.service';
// import { GetAuthorArgs } from './dto/get-author.args';

const pubSub = new PubSub();

@Resolver(() => Author)
export class AuthorResolver {
  constructor(
     private authorsService: AuthorService
  ) {}
 // 根据id查询作者信息
 @Query(returns => Author, {
    name: 'author',
    description: 'get author info by id',
    nullable: false
 })
 async getAuthor(@Args('id', {
     type: () => Int,
     description: 'author id',
     nullable: false
 }) id: number): Promise<any> {
 // return this.authorsService.findOneById(id);
    return {
        id,
        firstName: 'wu',
        lastName: 'pat',
    };
}
// 使用DTO接受参数
// @Query(returns => Author)
// async getAuthor(@Args() args: GetAuthorArgs) {
//   return this.authorsService.findOneById(args);
// }
 // 修改作者信息
 @Mutation(returns => Author, {
    name: 'changeAuthor',
    description: 'change author info by id',
    nullable: false
 })
 async changeAuthor(
    @Args('id') id: number,
    @Args('firstName') firstName: string,
    @Args('lastName') lastName: string,
 ): Promise<any> {
 // return this.authorsService.findOneById(id);
 return {
    id,
    firstName,
    lastName,
  };
}

 // 解析posts字段
 @ResolveField()
 async posts(@Parent() author: Author): Promise<any> {
     const { id } = author;
     // return this.postsService.findAll({ authorId: id });
     return [{
        id: 4,
        title: 'hello',
        votes: 2412,
     }];
 }
 
 // 新增文章
 @Mutation(returns => Post)
 async addPost() {
     const newPost = {
        id: 1,
        title: '新增文章'
     };
     // 新增成功后,通知更新
     await pubSub.publish('postAdded', { postAdded: newPost });
     return newPost;
 }
 
 // 监听变更
 @Subscription(returns => Post, {
     name: 'postAdded',
     // filter: (payload, variables) => payload.postAdded.title === variables.title,
     // 过滤订阅
     // resolve(this: AuthorResolver, value) { // 修改payload参数
     //   return value;
     // } })
 async postAdded(/*@Args('title') title: string*/) {
    return (await pubSub.asyncIterator('postAdded'));
 }}
// author.model.ts
import { Field, Int, ObjectType } from '@nestjs/graphql';
import { Post } from './post.model';

@ObjectType({ description: 'Author model' })
export class Author {
 @Field(type => Int, {
    description: '作者id'
 })
 id: number;
 
 @Field({
    nullable: true,
    description: '作者姓姓氏'
 })
 firstName?: string;
 
 @Field({ 
    nullable: true,
    description: '作者姓名字'
 })
 lastName?: string;
 
 // 要声明数组的项(而不是数组本身)是可为空的,请将nullable属性设置'items'
 // 如果数组及其项都是可空的,则设置nullable为'itemsAndList' 
 @Field(type => [Post], {
    nullable: 'items',
    description: '作者发表的文章'
 })
 posts: Post[];
}
// posts.model.ts
import { Field, Int, ObjectType } from '@nestjs/graphql';

@ObjectType()
export class Post {

 @Field(type => Int)
 id: number;
 
 @Field() title: string;
 
 @Field(type => Int, {
    nullable: true
 })
 votes?: number;
}

上面的代码包含了查询、变更、订阅类型,此时我们会发现src下面新增了一个文件schema.gql,这个文件就是自动生成的类型文件:

# ------------------------------------------------------
# THIS FILE WAS AUTOMATICALLY GENERATED (DO NOT MODIFY)
# ------------------------------------------------------
type Post {
    id: Int!
    title: String!
    votes: Int
}

"""Author model"""
type Author {
    """作者id"""
    id: Int!
    
    """作者姓姓氏"""
    firstName: String
    
    """作者姓名字"""
    lastName: String
    
    """作者发表的文章"""
    posts: [Post]!
}

type Query {
    """get author info by id"""
    author(
        """author id"""
        id: Int!
    ): Author!
}

type Mutation {
    """change author info by id""" 
    changeAuthor(lastName: String!, firstName: String!, id: Float!): Author!
    addPost: Post!
}

type Subscription {
    postAdded: Post!
}

执行查询

这时我们的服务已经运行起来,可以执行查询了。
image

# 左下角编写QUERY VARIABLES
{
    "id": 1
}
# Write your query or mutation here
# 查询作者信息
query author($id: Int!) {
    alias: author(id: $id) {
        id,
        firstName,
        posts {
            id,
            title
        }
    }
}

# 修改作者信息
mutation changeAuthor {
    changeAuthor(id: 3, firstName: "firstName" lastName: "lastName") {
        id,
        firstName,
        lastName
    }
}

# 发布文章
mutation addPost {
    post: addPost {
        id,
        title
    }
}

# 订阅文章新增
subscription postAdded{
    postAdded {
        id,
        title
    }
}

// 自省查询
query schema{
    __schema {
        types { 
            name
        }
    }
}

至此,我们的Nestjs+GraphQL服务便搭建完成,给自己一个👍!

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