如何在反應 state 中將元素推入數組，數組位於 object 內部

Question

將 object 推入數據中的問題數組中，它會給出此錯誤 Uncaught TypeError: data.sections is not iterable at handleClick (SecondStep.tsx:14:1)

 export default function CreateStepper() { const [data, setData] = useState({ name: "", desc: "", sections: [], }); console.log(data); return ( <><SecondStep data={data} setData={setData} /></>) } function SecondStep(data: any, setData: any) { const [addSection, setAddSection] = useState(1); const newSection = { sectionName: "Hdsd", sectionDesc: "dsdsd", question: [], }; const handleClick = () => { setData({...data, sections: [...data.sections, newSection] }); }; return ( <Box> </Box> ); } export default SecondStep;

當我執行下面的代碼時，它會返回“Uncaught TypeError: Cannot read properties of undefined (reading 'push')”這個類型錯誤。 如何將新的 object 推送到 React useState 中的數組。 首先useState是object里面的object有疑問：【數組如何推入object這個數組】

 const [data, setData] = useState({ name: "", desc: "", sections: [], }); const newSection = { sectionName: "Hello", sectionDesc: "Desc", question: [], }; const handleClick = () => { let copyData = data; copyData.sections.push(newSection); setData(copyData); };

Answer 1

您可以在 setState 方法中獲取最新版本的 state，然后您可以在其中添加您的 object。

const [data, setData] = useState({
    name: "",
    desc: "",
    sections: [],
 });

const newSection = {
    sectionName: "Hello",
    sectionDesc: "Desc",
    question: [],
};

const handleClick = () => {
   setData(data => ({
     ...data,
     sections: [...data.sections, newSection]
   })
 };

但我實際上不太確定您是否需要...data ，您可以將其排除在外。

Answer 2

您必須克隆 object 然后將元素推送到數組中，

這是下面的示例，

import "./styles.css";
import React, {useState} from 'react'

export default function App() {

  const [data, setData] = useState({
    name: "",
    desc: "",
    sections: [],
 });

const newSection = {
    sectionName: "Hello",
    sectionDesc: "Desc",
    question: [],
};

const handleClick = () => {
   setData({...data, sections:[...data.sections, newSection]});
 };

  return (
    <div className="App">
      <h1>Hello CodeSandbox</h1>
      <button onClick={handleClick}>Click</button>
      <h4>Sections: {data.sections[0]?.sectionName}</h4>

    </div>
  );
}

代碼沙箱： https://codesandbox.io/s/react-do7bk?file=/src/App.js:0-572

Answer 3

更新問題的答案是：

import "./styles.css";
import React, { useState } from "react";

export const CreateStepper = () => {
  const [data, setData] = useState({
    name: "",
    desc: "",
    sections: []
  });

  const SecondStep = (data: any) => {
    const [addSection, setAddSection] = useState(1);
    const newSection = {
      sectionName: "Hdsd",
      sectionDesc: "dsdsd",
      question: []
    };

    const handleClick = () => {
      setData({ ...data, sections: [...data.sections, newSection] });
    };

    return <></>;
  };

  return (
    <>
      <SecondStep data={data} />
    </>
  );
};

export default CreateStepper;

您還可以通過道具為 SecondStep 提供 function 如果您願意，這應該可以：

export default function CreateStepper() {
  const [data, setData] = useState({
    name: "",
    desc: "",
    sections: [],
  });

  console.log(data);

  return (
    <><SecondStep data={data} setData={setData} /></>)
}


function SecondStep(data: any, setData: (data : any) => void) {
  const [addSection, setAddSection] = useState(1);
  const newSection = {
    sectionName: "Hdsd",
    sectionDesc: "dsdsd",
    question: [],
  };

  const handleClick = () => {
    props.setData({ ...data, sections: [...data.sections, newSection] });
  };

  return (
    <Box>
      
    </Box>
  );
}

export default SecondStep;