如何在调用 Apollo Graph QL Query 之前等待服务器响应？

Question

从我的 useEffect 挂钩接收数据后，我试图调用 Graph QL 查询。我需要响应中的数据才能在查询中使用。但是不能有条件地调用钩子。但是，如果我取消条件，loadedAnime 将是未定义的。我如何绕过这种限制？

import React, { useEffect, useState } from "react";

import { useParams } from "react-router-dom";

import AnimeBanner from "../components/AnimeBanner";

import { useHttpClient } from "../Hooks/http-hook";

import { GetAnimeData } from "../GraphQLFunctions";

import { useQuery } from "@apollo/react-hooks";

import gql from "graphql-tag";

const GET_ANIME_INFO = gql`

  query GetAnimeInfo($name: String!) {

    Media(search: $name) {

      title {

        romaji

        english

        native

        userPreferred

      }

      episodes

      id

      bannerImage

    }

  }

`;

const Anime = (props) => {

  //Logic for getting anime data from mongoDB (episodes, name, cover image)

  const { isLoading, error, sendRequest } = useHttpClient();

  const [loadedAnime, setloadedAnime] = useState();

  const URLTitle = useParams().URLTitle;

  useEffect(() => {

    const fetchAnime = async () => {

      try {

        const responseData = await sendRequest(

          "http://localhost:5000/api/anime/" + URLTitle

        );

        setloadedAnime(responseData.animeData[0]);

      } catch (err) {

        console.log(err);

      }

    };

    fetchAnime();

  }, [sendRequest, URLTitle]);

  if (isLoading || error) {

    return null;

  }

  //Logic for getting anime data from anilist (Descriptions, tags, banner, trailer, etc.)

  const { apiData, apiLoading, apiError } = useQuery(GET_ANIME_INFO, {

    variables: {

      name: loadedAnime.anime_name,

    },

  });

  if (apiLoading || apiError) {

    return null;

  }

  return <AnimeBanner src={apiData.Media.bannerImage} />;

};

export default Anime;

Answer 1

简短回答：您可以签出 useLazyQuery 而不是 useQuery。文档链接：https ://www.apollographql.com/docs/react/data/queries/#executing-queries-manually当 React 挂载并渲染调用 useQuery 钩子的组件时，Apollo Client 会自动执行指定的查询。但是，如果您想要执行查询以响应不同的事件（例如用户单击按钮）怎么办？useLazyQuery 挂钩非常适合执行查询以响应组件呈现以外的事件。这个钩子就像 useQuery 一样，有一个关键的例外：调用 useLazyQuery 时，它不会立即执行其关联的查询。相反，它在其结果元组中返回一个函数，您可以在准备好执行查询时调用该函数import React, { useState } from 'react';import { useLazyQuery } from '@apollo/client';function DelayedQuery() {&nbsp; const [dog, setDog] = useState(null);&nbsp; const [getDog, { loading, data }] = useLazyQuery(GET_DOG_PHOTO);&nbsp; if (loading) return <p>Loading ...</p>;&nbsp; if (data && data.dog) {&nbsp; &nbsp; setDog(data.dog);&nbsp; }&nbsp; return (&nbsp; &nbsp; <div>&nbsp; &nbsp; &nbsp; {dog && <img src={dog.displayImage} />}&nbsp; &nbsp; &nbsp; <button onClick={() => getDog({ variables: { breed: 'bulldog' } })}>&nbsp; &nbsp; &nbsp; &nbsp; Click me!&nbsp; &nbsp; &nbsp; </button>&nbsp; &nbsp; </div>&nbsp; );}

Answer 2

您可以在完成后调用查询，也可以在 api 调用后更新状态后调用await另一个查询。useEffect一般来说，像这样的东西，const [state, setState] = useState({})useEffect(async () => {&nbsp; &nbsp; const result = await get('/api/blah-blah-blah')&nbsp; &nbsp; // run your query here now that the await has resolved}, [someDependency])或者const [state, setState] = useState({})useEffect(async () => {&nbsp; &nbsp; const result = await get('/api/blah-blah-blah')&nbsp; &nbsp; setState(result)}, [someDependency])useEffect(() => {&nbsp; &nbsp;if(state.id) {&nbsp; &nbsp; &nbsp; &nbsp;// run the query&nbsp; &nbsp;}}, [state.someProp])