如何在调用 Apollo Graphql Query 之前等待服务器响应？

Question

我在从我的 useEffect 挂钩接收数据后尝试调用 Graph QL 查询。我需要响应中的数据才能在查询中使用。然而，钩子不能有条件地调用。但是，如果我取消条件，loadedAnime 将是未定义的。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 挂载并渲染一个调用 useQuery 钩子的组件时，Apollo Client 会自动执行指定的查询。但是，如果您想执行查询以响应不同的事件，例如用户单击按钮，该怎么办？

useLazyQuery 钩子非常适合执行查询以响应组件渲染以外的事件。这个钩子就像 useQuery 一样，有一个关键的例外：当 useLazyQuery 被调用时，它不会立即执行其关联的查询。相反，它会在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() {
  const [dog, setDog] = useState(null);
  const [getDog, { loading, data }] = useLazyQuery(GET_DOG_PHOTO);

  if (loading) return <p>Loading ...</p>;

  if (data && data.dog) {
    setDog(data.dog);
  }

  return (
    <div>
      {dog && <img src={dog.displayImage} />}
      <button onClick={() => getDog({ variables: { breed: 'bulldog' } })}>
        Click me!
      </button>
    </div>
  );
}

Answer 2

您可以在 await 完成后调用查询，也可以在 api 调用后更新状态后在另一个 useEffect 中调用您的查询。一般来说，像这样，

const [state, setState] = useState({})

useEffect(async () => {
    const result = await get('/api/blah-blah-blah')

    // run your query here now that the await has resolved
}, [someDependency])

或

const [state, setState] = useState({})

useEffect(async () => {
    const result = await get('/api/blah-blah-blah')

    setState(result)
}, [someDependency])

useEffect(() => {
   if(state.id) {
       // run the query
   }
}, [state.someProp])