如何在 type-graphql 中触发订阅？答案

【问题标题】：How to trigger subscriptions in type-graphql?如何在 type-graphql 中触发订阅？
【发布时间】：2021-01-14 03:09:38
【问题描述】：

我有一个使用 Apollo Server 和 express 建立的项目。我一直在尝试设置订阅，但它没有发生。我已按照以下链接执行所有步骤：

https://typegraphql.com/docs/subscriptions.html

此外，我最初运行订阅时无法收听。所以我用一个 http 服务器包装了我的 express 应用程序，在我的 app.listen 中，我添加了一个新的订阅服务器，然后订阅正在监听。但是现在，当我运行应该触发订阅的突变时，它不会被触发。我一直在尝试很多东西，但到目前为止，SO 或 Github 上没有任何帮助。

以下是服务器的代码


import express from "express";
import { ApolloServer } from "apollo-server-express";
import cors from "cors";
import { SubscriptionServer } from "subscriptions-transport-ws";
import { execute, subscribe } from "graphql";
import { createServer } from "http";

const main = () => {
  const app = express();

  app.use(
    cors({
      origin: "http://localhost:3000",
      credentials: true,
    })
  );
  const apolloServer = new ApolloServer({
    playground: {
      settings: {
        "request.credentials": "include",
      },
    },
    schema: await buildSchema({
      resolvers: [Resolver1, Resolver2, Resolver3],
      validate: false,
    }),
    context: ({ req, res }) => ({ req, res, redis }),
  });

  apolloServer.applyMiddleware({
    app,
    cors: false,
  });

  const server = createServer(app);

  server.listen(4000, async () => {
    console.log("Server running on port 4000");
    new SubscriptionServer(
      {
        execute,
        subscribe,
        schema: await buildSchema({
          resolvers: [Resolver1, Resolver2, Resolver3],
          validate: false,
        }),
      },
      {
        server,
        path: "/graphql",
      }
    );
  });
};

如果我做错了什么，请告诉我或引导我朝着正确的方向前进。

【问题讨论】：

我也遇到了同样的问题，您找到可行的解决方案了吗？如果是这样，请在这里分享。

标签： typescript graphql apollo-server graphql-subscriptions typegraphql

【解决方案1】：

应该这样做：-

import 'reflect-metadata';
import express from 'express';
import { ApolloServer } from 'apollo-server-express';
import { devLogger } from './utils/constants';
import { createServer } from 'http';
import { getSchema } from './utils/schema';

const main = async () =>
{
    const app = express();
    const ws = createServer( app );
    const apolloServer = new ApolloServer( {
        schema: await getSchema(),

    } );

    apolloServer.applyMiddleware( { app } );
    apolloServer.installSubscriptionHandlers( ws );

    const PORT = process.env.PORT || 5000;
    ws.listen( PORT, async () =>
    {
        devLogger( `Server started on port ${ PORT }` );
    } );
};

main().catch( err => devLogger( err ) );

【讨论】：

【解决方案2】：

您不需要从 subscriptions-transport-ws 导入 SubscriptionServer。这是一个简单的 GraphQL 服务器模板。

server.ts

import "reflect-metadata";
import express from "express";
import { ApolloServer } from "apollo-server-express";
import { buildSchema } from "type-graphql";
import http from 'http';

const main = async () => {
  const app = express();
  const httpServer = http.createServer(app)

  const apolloServer = new ApolloServer({
    schema: await buildSchema({
      // Insert your resolvers here
      resolvers: [],
      validate: false
    }),
    // Not required but if you want to change your path do it here. The default path is graphql if "subscriptions" field is not passed
    subscriptions: {
      path: "/subscriptions",
      onConnect: () => console.log("Client connected for subscriptions"),
      onDisconnect: () => console.log("Client disconnected from subscriptions")
    }
  });

  apolloServer.applyMiddleware({ app, cors: false });
  apolloServer.installSubscriptionHandlers(httpServer)

  httpServer.listen(4000, () => console.log("Server ready at http://localhost:4000"))
};

main().catch((err) => console.error(err));

解析器

import {
  Arg,
  Mutation,
  Resolver,
  Root,

  // Required for subscription to work
  Subscription, 
  PubSub,
  PubSubEngine
} from "type-graphql";

@Resolver()
export class MessageResolver {
  @Subscription({ topics: 'NOTIFICATIONS' })
  newNotification(@Root() payload: string) : string {
    return payload
  }

  @Mutation(() => String)
  async sendMessage(
    @Arg('name') name: string,
    @PubSub() pubsub: PubSubEngine
  ): Promise<string> {
    pubsub.publish('NOTIFICATIONS', name)
    return name
  }
}

注意要回答您的问题，Typescript 很可能没有读取您编写订阅解析器的文件，从而导致没有创建 GraphQL 模式。确保将以下行添加到您的 tsconfig.json 文件中。有时，vscode 会自动导入路径并将它们添加到这一行。

  "include": [
    "./src/**/*.tsx",
    "./src/**/*.ts"
  ]

【讨论】：