graphQL 订阅返回 null

如何解决graphQL 订阅返回 null

我正在开发一个聊天应用程序，但遇到 graphql 订阅返回 null 的问题。我查看了其他类似/相同的主题，但不幸的是它没有帮助我。 查询和变异工作正常。

谁能告诉我我做错了什么？

Server.ts：

const { GraphQLServer,PubSub } = require("graphql-yoga");

const chat = [
  {
    id: 0,name: "Beer group",messages: [
      {
        user: {
          name: "PJ",profilePic: "PJ pic",},body: "hey mates! Beer tonight?",],{
    id: 1,name: "Bikes group",messages: [
      {
        user: {
          name: "MJ",profilePic: "MJ pic",body: "Ride tomorrow morning?",];

const typeDefs = `

type Query {
  rooms: [RoomsType]
  messages(roomID: String!): [SingleMessageType]
}

type Mutation {
postMessage(user: String!,body: String!,roomID: String!): ID!
createRoom(name: String!): ID!
}

type Subscription {
  messageAdded(roomID: String!): [SingleMessageType]
}

type RoomsType {
  id: String
  name: String
}

type SingleMessageType {
  user: SingleUserType
  body: String
}

type SingleUserType {
  name: String
  profilePic: String
}
`;

const subscribers = [];
const onRoomsUpdates = (fn) => subscribers.push(fn);

const resolvers = {
  Query: {
    rooms: () => chat,messages: (parent,{ roomID }) => chat[roomID].messages,Mutation: {
    postMessage: (parent,{ user,body,roomID }) => {
      // const id = rooms[roomID].messages.length;
      chat[roomID].messages.push({
        user: {
          name: user,profilePic: "USER pic",body: body,});
      subscribers.forEach((fn) => fn());
      return roomID;
    },createRoom: (parent,{ name }) => {
      const id = rooms.length;
      const messages = [];
      chat.push({ id,name,messages });
      return id;
    },Subscription: {
    messageAdded: {
      subscribe: (parent,args,{ pubsub,body }) => {
        const channel = Math.random().toString(36).slice(2,15);
        onRoomsUpdates(() =>
          pubsub.publish(channel,{
            messages: [{ user: { name: name,profilePic: "" },body: body }],})
        );
        setTimeout(
          () =>
            pubsub.publish(channel,{
              messages: [{ user: { name: name,}),0
        );
        return pubsub.asyncIterator(channel);
      },};

const pubsub = new PubSub();
const server = new GraphQLServer({ typeDefs,resolvers,context: { pubsub } });
server.start(({ port }) => {
  console.log(`Server on http://localhost:${port}/`);
});

查询.ts：

import { gql } from "@apollo/client";

const GET_ROOMS = gql`
  query GetRooms {
    rooms {
      id
      name
    }
  }
`;

const GET_MESSAGES = gql`
  query GetMessages($roomID: String!) {
    messages(roomID: $roomID) {
      user {
        name
        profilePic
      }
      body
    }
  }
`;

const POST_MESSAGE = gql`
  mutation postMessage($user: String!,$roomID: String!,$body: String!) {
    postMessage(user: $user,roomID: $roomID,body: $body)
  }
`;

const MESSAGE_SUBSCRIPTION = gql`
  subscription messageAdded($roomID: String!) {
    messageAdded(roomID: $roomID) {
      user {
        name
        profilePic
      }
      body
    }
  }
`;

export { GET_ROOMS,GET_MESSAGES,POST_MESSAGE,MESSAGE_SUBSCRIPTION };

RoomScreen.tsx：

import React from "react";
import { Text,View } from "react-native";
import "react-native-gesture-handler";
import {
  GET_MESSAGES,MESSAGE_SUBSCRIPTION,// GET_ROOMS,} from "./Querries";
import { useQuery,useMutation } from "@apollo/client";
// import PostMessage from "./PostMessage";
import { GiftedChat } from "react-native-gifted-chat";
import { styles } from "./styles";
// import { login } from "../misc/crede";

export default function RoomScreen(props) {
  const roomID = props.route.params.roomID;
  const [postMessage] = useMutation(POST_MESSAGE);
  const { data,loading,error,subscribetoMore } = useQuery(GET_MESSAGES,{
    variables: { roomID: roomID },});

  if (loading) return <Text>Loading...</Text>;
  if (error) return <Text>Error :(</Text>;

  subscribetoMore({
    document: MESSAGE_SUBSCRIPTION,variables: { roomID: roomID },updateQuery: (prev,{ subscriptionData }) => {
      if (!subscriptionData.data) return prev;
      const newFeedItem = subscriptionData.data;
      return Object.assign({},prev,{
        chat: {
          ...prev.chat,messages: [...prev.messages,newFeedItem],});
    },});

  return (
    <View style={styles.container}>
      <GiftedChat
        messages={data.messages.map((msg) => ({
          // _id: msg.id,text: msg.body,user: {
            _id: msg.user.name,name: msg.user.name,avatar: msg.user.profilePic,}))}
        onSend={(e) => {
          postMessage({
            variables: {
              body: e[0].text,roomID: roomID,user: "User",// password: login.password,});
        }}
        user={{ _id: "User" }}
        inverted={false}
        showUserAvatar={false}
        renderUsernameOnMessage={true}
      />
    </View>
  );
}

完整代码在此链接下：https://github.com/PatrykJamroz/chat-app/tree/local-graphql-remove-phoenix-2