我的状态没有使用 React Hooks 更新

3回答

倚天杖

我的问题的解决方法是它没有重新渲染，所以它一直落后于整个时间。在 useEffect 中添加状态作为依赖项可以解决问题！我希望这可以帮助其他有类似问题的人，以某种方式帮助社区。import React, { createContext, useState, useEffect } from "react";import items from "../data";export const RoomContext = createContext();const RoomProvider = (props) => {  const [rooms, setRooms] = useState([]);  const [sortedRooms, setSortedRooms] = useState([]);  const [featuredRooms, setFeaturedRooms] = useState([]);  const [loading, setLoading] = useState(true);  const [type, setType] = useState("all");  const [capacity, setCapacity] = useState(1);  const [price, setPrice] = useState(0);  const [minPrice, setMinPrice] = useState(0);  const [maxPrice, setMaxPrice] = useState(0);  const [minSize, setMinSize] = useState(0);  const [maxSize, setMaxSize] = useState(0);  const [breakfast, setBreakfast] = useState(false);  const [pets, setPets] = useState(false);  //call the formatted data  useEffect(() => {    //set rooms    const rooms = formatData(items);    //set the featured rooms    const featuredRooms = rooms.filter((room) => room.featured === true);    //always show the max price as default    const maxPrice = Math.max(...rooms.map((item) => item.price));    //always show the max price as default    const maxSize = Math.max(...rooms.map((item) => item.size));    setRooms(rooms);    setSortedRooms(rooms);    setFeaturedRooms(featuredRooms);    setLoading(false);    setMaxPrice(maxPrice);    setMaxSize(maxSize);    setPrice(maxPrice);  }, [    type,    capacity,    price,    minPrice,    maxPrice,    minSize,    maxSize,    breakfast,    pets,  ]);  //format data is getting all the required fields we want to pull from the originl data  const formatData = (items) => {    let tempItems = items.map((item) => {      const id = item.sys.id;      const images = item.fields.images.map((image) => image.fields.file.url);      const room = { ...item.fields, images: images, id: id };      return room;    });    return tempItems;  };  const getRoom = (slug) => {    let tempRooms = [...rooms];    const room = tempRooms.find((room) => room.slug === slug);    return room;  };  const handleChange = (e) => {    const target = e.target;    const value = e.type === "checkbox" ? target.checked : target.value;    const name = e.target.name;    switch (name) {      case "type":        setType(value);        break;      case "capacity":        setCapacity(value);        break;      case "price":        setPrice(value);        break;      case "minPrice":        setMinPrice(value);        break;      case "maxPrice":        setMaxPrice(value);        break;      case "minSize":        setMinSize(value);        break;      case "maxSize":        setMaxSize(value);        break;      case "breakfast":        setBreakfast(value);        break;      case "pets":        setPets(value);        break;      default:        return;    }    console.log(name, value);  };  const filteredRooms = () => {    let initialRooms = [...rooms];    if (type !== "all") {      initialRooms = initialRooms.filter((room) => room.type === type);    }    console.log("room type is", type);    setSortedRooms(initialRooms);  };  return (    <RoomContext.Provider      value={{        rooms,        featuredRooms,        getRoom,        loading,        sortedRooms,        type,        capacity,        price,        minPrice,        maxPrice,        minSize,        maxSize,        breakfast,        pets,        handleChange,        filteredRooms,      }}    >      {props.children}    </RoomContext.Provider>  );};export default RoomProvider;

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桃花长相依

欢迎来到 SO。您仍然可以编写this.setState与 useState 提供的示例类似的代码。这是一个可快速运行的示例。围绕您的项目的答案：创建一个使用 useContext 的组件，只需加载您需要的值和 handleChange 方法const Test = () => {  const { type, capacity, handleChange } = React.useContext(RoomContext);  console.log(type, capacity);  return (      <div>         <select name="type" onChange={handleChange}>             <option value="all">all</option>             <option value="another">another</option>             <option value="one">one</option>         </select>         <select name="capacity" onChange={handleChange}>           <option value="1">1</option>           <option value="50">50</option>           <option value="100">100</option>         </select>       </div>   ) };添加 Test 组件作为 Room Provider 的子组件。启动应用程序，您应该会看到它会正常更新工作可运行示例：const target = e.target;const value = e.type === "checkbox" ? target.checked : target.value;const name = e.target.name;    this.setState({ [name]: value });const rootEl = document.getElementById('root');const App = () => {  const [form, setForm] = React.useState({    name: '',    checkbox: false,  });    const handleChange = (e) => {    const target = e.target;    const value = e.type === "checkbox" ? target.checked : target.value;    const name = e.target.name;        setForm(prevState => ({ ...prevState, [name]: value }));  }    return (    <div>      <label>Name</label>      <input type="text" name="name" value={form.name} onChange={handleChange} />      <label>Checkbox</label>      <input type="checkbox" name="checkbox" checked={form.checkbox} onChange={handleChange} />      <pre>{JSON.stringify(form)}</pre>    </div>  )}ReactDOM.render(<App />, rootEl);<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js"></script><div id="root"></div>这是具有多个 useState 的代码的运行示例。const rootEl = document.getElementById('root');const App = () => {  const [name, setName] = React.useState('');  const [checkbox, setCheckbox] = React.useState(false);  const handleChange = (e) => {    const target = e.target;    const value = e.type === "checkbox" ? target.checked : target.value;    const name = e.target.name;        switch (name) {      case "name":        setName(value);        break;      case "checkbox":        setCheckbox(value);        break;      default:        return;    }  };    return (    <div>      <label>Name</label>      <input type="text" name="name" value={name} onChange={handleChange} />      <label>Checkbox</label>      <input type="checkbox" name="checkbox" checked={checkbox} onChange={handleChange} />      <pre>{JSON.stringify({ name, checkbox })}</pre>    </div>  )}ReactDOM.render(<App />, rootEl);<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js"></script><div id="root"></div>

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函数式编程

你导入 useState 了吗？import React, {useState} from 'react';

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