React useState - 將變量保存到本地存儲

Question

我是 React 和 state 鈎子的新手。我正在嘗試創建一個關於創建書單並將其保存到本地存儲的網站。 還將圖像上傳到cloudinary。 我的問題是； 當我嘗試將雲圖像 url 保存到本地存儲時，它會保存以前的 url。 我想我對 useState 鈎子有疑問，但我想不通。 下面是我的代碼。

LocalStorage.js

import React, { useState, useEffect } from 'react'
import BookList from '../../components/BookList'
import CreateBook from '../../components/CreateBook'

const getLocalStorage = () => {
  let list = localStorage.getItem('liste')
  if (list) {
    return JSON.parse(localStorage.getItem('liste'))
  } else {
    return []
  }
}

const LocalStorage = () => {
  //state hooks
  const [list, setList] = useState(getLocalStorage)
  const [bookName, setBookName] = useState('')
  const [writerName, setWriterName] = useState('')
  const [pageNumber, setPageNumber] = useState('')
  const [info, setInfo] = useState('')
  const [image, setImage] = useState('')
  const [uploadUrl, setUploadUrl] = useState('')
  let id


  //Function for submit button
  const handleSubmit = async (e) => {
    e.preventDefault()
    // conditions for fill the blanks
    if (!bookName || !writerName || !pageNumber || !image) {
      setInfo('Please fill the blanks')
    } else {
      try {
        const data = new FormData()
        data.append('file', image)
        data.append('upload_preset', 'book-list-project')
        data.append('cloud_name', 'book-list')
        let response = await fetch(
          'https://api.cloudinary.com/v1_1/book-list/image/upload',
          {
            method: 'POST',
            body: data,
          }
        )
        let result = await response.json()
        setUploadUrl(result.url)
        id = new Date().getTime().toString()
        const newBook = {
          id: id,
          bookName: bookName,
          writerName: writerName,
          pageNumber: pageNumber,
          uploadUrl: uploadUrl,
        }

        setList([...list, newBook])
        setBookName('')
        setWriterName('')
        setPageNumber('')
        setInfo('Book created')
        setImage('')
      } catch (error) {
        console.log(error)
      }
    }
  }

  //Function for remove specific book from local storage
  const removeSpecificBook = (id) => {
    setList(list.filter((book) => book.id !== id))
  }

  // Function for clear all books from local storage
  const removeAllBooks = () => {
    setList([])
  }

  useEffect(() => {
    localStorage.setItem('liste', JSON.stringify(list))
  }, [list])

  return (
    <div>
      <CreateBook
        bookName={bookName}
        writerName={writerName}
        pageNumber={pageNumber}
        handleSubmit={handleSubmit}
        info={info}
        setBookName={setBookName}
        setWriterName={setWriterName}
        setPageNumber={setPageNumber}
        setImage={setImage}
      />

      <BookList
        items={list}
        removeSpecificBook={removeSpecificBook}
        removeAllBooks={removeAllBooks}
      />
    </div>
  )
}

export default LocalStorage

Booklist.js

import React from 'react'

const BookList = ({ items, removeSpecificBook, removeAllBooks }) => {
  return (
    <div className='container mx-auto'>
      <div className='mt-20 flex flex-wrap items-center justify-center'>
        {items.map((item) => {
          return (
            <div key={item.id} className='p-2 m-2 bg-yellow-100 w-1/4'>
              <div className='p-1 m-1 flex justify-center'>
                <img
                  className='object-contain h-52 w-52'
                  src={item.uploadUrl}
                  alt='some img'
                />
              </div>
              <div className='p-1 m-1'>
                <h5 className='font-semibold'>Book Name</h5>
                <h3>{item.bookName}</h3>
              </div>
              <div className='p-1 m-1'>
                <h5 className='font-semibold'>Writer Name</h5>
                <h3>{item.writerName}</h3>
              </div>
              <div className='p-1 m-1'>
                <h5 className='font-semibold'>Total Page</h5>
                <h3>{item.pageNumber}</h3>
              </div>
              <div className='flex justify-end'>
                <button
                  onClick={() => removeSpecificBook(item.id)}
                  className='px-4 py-2 bg-red-500 rounded-full text-white'
                >
                  Remove
                </button>
              </div>
            </div>
          )
        })}
      </div>
      {items.length > 1 && (
        <div className='flex justify-center my-5'>
          <button
            onClick={removeAllBooks}
            className='px-8 py-4 bg-red-500 rounded-full text-white'
          >
            Remove All
          </button>
        </div>
      )}
    </div>
  )
}

export default BookList

CreateBook.js

import React from 'react'

const CreateBook = ({
  bookName,
  writerName,
  pageNumber,
  handleSubmit,
  info,
  setBookName,
  setWriterName,
  setPageNumber,
  setImage,
}) => {
  return (
    <div>
      <div>
        <nav className='bg-blue-500  text-center text-white px-6 py-3'>
          Create Book
        </nav>
      </div>
      <div className='bg-red-200 mx-auto w-96 rounded-lg flex justify-center mt-20'>
        <form onSubmit={handleSubmit}>
          <div>
            <div className='p-3 text-center'>
              <h6>Enter Book Name</h6>
              <input
                value={bookName}
                onChange={(e) => setBookName(e.target.value)}
                className='rounded-md'
                type='text'
                placeholder='Book Name'
              />
            </div>
            <div className='p-3 text-center'>
              <h6>Enter Writer Name</h6>
              <input
                value={writerName}
                onChange={(e) => setWriterName(e.target.value)}
                className='rounded-md'
                type='text'
                placeholder='Writer Name'
              />
            </div>
            <div className='p-3 text-center'>
              <h6>Enter Total Page Number </h6>
              <input
                value={pageNumber}
                onChange={(e) => setPageNumber(e.target.value)}
                className='rounded-md'
                type='number'
                placeholder='Page Number'
              />
            </div>
            <div className='p-3 text-center'>
              <div>
                <h6>Upload Image</h6>
              </div>
              <div className='p-3'>
                <input
                  type='file'
                  onChange={(e) => setImage(e.target.files[0])}
                />
              </div>
            </div>
            <div className='flex justify-center p-3'>
              <button className='bg-blue-500 py-3 px-6 rounded-full text-white'>
                Submit
              </button>
            </div>
            <div className='p-3 text-center  text-white'>
              <h3>{info}</h3>
            </div>
          </div>
        </form>
      </div>
    </div>
  )
}

export default CreateBook

如果您對我的代碼結構有任何建議，請告訴我。 我沒有任何編程歷史並試圖從頭開始學習。 我需要對 go 進一步學習編程的所有建議。 先感謝您。

Answer 1

setUploadUrl(result.url);
id = new Date().getTime().toString();
const newBook = {
  id: id,
  bookName: bookName,
  writerName: writerName,
  pageNumber: pageNumber,
  uploadUrl: uploadUrl
};

在這里，您將uploadUrl 更新為newBook object。 但是uploadUrl的值保持了之前的記錄。 不要從 uploadUrl 設置，而是從result.url設置。