属性"handle"在类型 "undefined" 上不存在 - 反应上下文和打字稿

Question

我正在将我的应用程序从JS转换为TS.一切都在JS下工作得很好，但当开始转换为TS时，我得到了大量的错误处理函数，例如handleVideoAdd。有人知道我哪里做错了吗?我做了很多尝试都没有成功。

属性'handleVideoAdd'不存在类型'undefined'。TS2339-它指向这段代码:

const { handleVideoAdd, inputURL, handleInputURLChange } = useContext(Context)

我的代码是这样的:

• Header.tsx

import { Context } from "../Context";
import React, { useContext } from "react";
import { Navbar, Button, Form, FormControl } from "react-bootstrap";
export default function Header() {
const { handleVideoAdd, inputURL, handleInputURLChange } =
useContext(Context);
return (
<Navbar bg="light" expand="lg">
<Navbar.Brand href="#home">Video App</Navbar.Brand>
<Form onSubmit={handleVideoAdd} inline>
<FormControl
type="text"
name="url"
placeholder="Paste url"
value={inputURL}
onChange={handleInputURLChange}
className="mr-sm-2"
/>
<Button type="submit" variant="outline-success">
Add
</Button>
</Form>
</Navbar>
);
}

• Context.tsx

import { useEffect, useMemo, useState } from "react";
import { youtubeApi } from "./APIs/youtubeAPI";
import { vimeoApi } from "./APIs/vimeoAPI";
import React from "react";
import type { FormEvent } from "react";
const Context = React.createContext(undefined);
function ContextProvider({ children }) {
const [inputURL, setInputURL] = useState("");
const [videoData, setVideoData] = useState(() => {
const videoData = localStorage.getItem("videoData");
if (videoData) {
return JSON.parse(videoData);
}
return [];
});
const [filterType, setFilterType] = useState("");
const [videoSources, setVideoSources] = useState([""]);
const [wasSortedBy, setWasSortedBy] = useState(false);
const [showVideoModal, setShowVideoModal] = useState(false);
const [modalData, setModalData] = useState({});
const [showWrongUrlModal, setShowWrongUrlModal] = useState(false);
const createModalSrc = (videoItem) => {
if (checkVideoSource(videoItem.id) === "youtube") {
setModalData({
src: `http://www.youtube.com/embed/${videoItem.id}`,
name: videoItem.name,
});
} else {
setModalData({
src: `https://player.vimeo.com/video/${videoItem.id}`,
name: videoItem.name,
});
}
};
const handleVideoModalShow = (videoID) => {
createModalSrc(videoID);
setShowVideoModal(true);
};
const handleVideoModalClose = () => setShowVideoModal(false);
const handleWrongUrlModalShow = () => setShowWrongUrlModal(true);
const handleWrongUrlModalClose = () => setShowWrongUrlModal(false);
const handleInputURLChange = (e) => {
setInputURL(e.currentTarget.value);
};
const handleVideoAdd = (e: FormEvent<HTMLFormElement>) => {
e.preventDefault();
const source = checkVideoSource(inputURL);
if (source === "youtube") {
handleYouTubeVideo(inputURL);
} else if (source === "vimeo") {
handleVimeoVideo(inputURL);
} else {
handleWrongUrlModalShow();
}
};
const checkVideoSource = (inputURL) => {
if (inputURL.includes("youtu") || inputURL.length === 11) {
return "youtube";
} else if (inputURL.includes("vimeo") || inputURL.length === 9) {
return "vimeo";
}
};
const checkURL = (inputURL) => {
if (!inputURL.includes("http")) {
const properURL = `https://${inputURL}`;
return properURL;
} else {
return inputURL;
}
};
const checkInputType = (inputURL) => {
if (!inputURL.includes("http") && inputURL.length === 11) {
return "id";
} else if (!inputURL.includes("http") && inputURL.length === 9) {
return "id";
} else {
return "url";
}
};
const fetchYouTubeData = async (videoID) => {
const data = await youtubeApi(videoID);
if (data.items.length === 0) {
handleWrongUrlModalShow();
} else {
setVideoData((state) => [
...state,
{
id: videoID,
key: `${videoID}${Math.random()}`,
name: data.items[0].snippet.title,
thumbnail: data.items[0].snippet.thumbnails.medium.url, //default, medium, high
viewCount: data.items[0].statistics.viewCount,
likeCount: data.items[0].statistics.likeCount,
savedDate: new Date(),
favourite: false,
source: "YouTube",
url: inputURL,
},
]);
setInputURL("");
}
};
const handleYouTubeVideo = (inputURL) => {
const inputType = checkInputType(inputURL);
if (inputType === "id") {
fetchYouTubeData(inputURL);
} else {
const checkedURL = checkURL(inputURL);
const url = new URL(checkedURL);
if (inputURL.includes("youtube.com")) {
const params = url.searchParams;
const videoID = params.get("v");
fetchYouTubeData(videoID);
} else {
const videoID = url.pathname.split("/");
fetchYouTubeData(videoID[1]);
}
}
};
const fetchVimeoData = async (videoID) => {
const data = await vimeoApi(videoID);
if (data.hasOwnProperty("error")) {
handleWrongUrlModalShow();
} else {
setVideoData((state) => [
...state,
{
id: videoID,
key: `${videoID}${Math.random()}`,
name: data.name,
thumbnail: data.pictures.sizes[2].link, //0-8
savedDate: new Date(),
viewCount: data.stats.plays,
likeCount: data.metadata.connections.likes.total,
savedDate: new Date(),
favourite: false,
source: "Vimeo",
url: inputURL,
},
]);
setInputURL("");
}
};
const handleVimeoVideo = (inputURL) => {
const inputType = checkInputType(inputURL);
if (inputType === "id") {
fetchVimeoData(inputURL);
} else {
const checkedURL = checkURL(inputURL);
const url = new URL(checkedURL);
const videoID = url.pathname.split("/");
fetchVimeoData(videoID[1]);
}
};
const deleteVideo = (key) => {
let newArray = [...videoData].filter((video) => video.key !== key);
setWasSortedBy(true);
setVideoData(newArray);
};
const deleteAllData = () => {
setVideoData([]);
};
const toggleFavourite = (key) => {
let newArray = [...videoData];
newArray.map((item) => {
if (item.key === key) {
item.favourite = !item.favourite;
}
});
setVideoData(newArray);
};
const handleFilterChange = (type) => {
setFilterType(type);
};
const sourceFiltering = useMemo(() => {
return filterType
? videoData.filter((item) => item.source === filterType)
: videoData;
}, [videoData, filterType]);
const sortDataBy = (sortBy) => {
if (wasSortedBy) {
const reversedArr = [...videoData].reverse();
setVideoData(reversedArr);
} else {
const sortedArr = [...videoData].sort((a, b) => b[sortBy] - a[sortBy]);
setWasSortedBy(true);
setVideoData(sortedArr);
}
};
const exportToJsonFile = () => {
let dataStr = JSON.stringify(videoData);
let dataUri =
"data:application/json;charset=utf-8," + encodeURIComponent(dataStr);
let exportFileDefaultName = "videoData.json";
let linkElement = document.createElement("a");
linkElement.setAttribute("href", dataUri);
linkElement.setAttribute("download", exportFileDefaultName);
linkElement.click();
};
const handleJsonImport = (e) => {
e.preventDefault();
const fileReader = new FileReader();
fileReader.readAsText(e.target.files[0], "UTF-8");
fileReader.onload = (e) => {
const convertedData = JSON.parse(e.target.result);
setVideoData([...convertedData]);
};
};
useEffect(() => {
localStorage.setItem("videoData", JSON.stringify(videoData));
}, [videoData]);
return (
<Context.Provider
value={{
inputURL,
videoData: sourceFiltering,
handleInputURLChange,
handleVideoAdd,
deleteVideo,
toggleFavourite,
handleFilterChange,
videoSources,
sortDataBy,
deleteAllData,
exportToJsonFile,
handleJsonImport,
handleVideoModalClose,
handleVideoModalShow,
showVideoModal,
modalData,
showWrongUrlModal,
handleWrongUrlModalShow,
handleWrongUrlModalClose,
}}
>
{children}
</Context.Provider>
);
}
export { ContextProvider, Context };

• App.js(尚未转换为TS)

import React from "react";
import ReactDOM from "react-dom";
import "./index.css";
import App from "./App";
import "bootstrap/dist/css/bootstrap.min.css";
import reportWebVitals from "./reportWebVitals";
import { ContextProvider } from "./Context.tsx";
ReactDOM.render(
<React.StrictMode>
<ContextProvider>
<App />
</ContextProvider>
</React.StrictMode>,
document.getElementById("root")
);
reportWebVitals();

Answer 1

这是因为您在创建上下文时将其默认为undefined。

这里发生:const Context = React.createContext(undefined)

你不能说undefined.handleVideoAdd。但理论上你可以说{}.handleVideoAdd。

如果你在开始的时候将上下文默认为{}，像这样:const Context = React.createContext({})

你的应用程序不应该再崩溃了。

编辑:我看到你在使用TypeScript，在这种情况下，你需要为你的context创建一个接口。像这样:

interface MyContext {
inputURL?: string,
videoData?: any,
handleInputURLChange?: () => void,
handleVideoAdd?: () => void,
deleteVideo?: () => void,
// and all the rest of your keys
}

然后在创建上下文时这样做:

const Context = React.createContext<MyContext>(undefined);