为使用的变量编译警告无未使用的变量

Question

所以我有一个 React 组件，SearchBooks它接收一个来自主App.js状态的数组books以及一个函数，onUpdateBooksState，也来自App.js。

一切正常，但我收到警告说两者都没有被使用，但它们是。

为什么我会收到这些警告，如何更正根本问题？

SearchBooks.js

import React, { Component } from 'react'
import * as BooksAPI from './utils/BooksAPI'
import Book from './Book';
export default class SearchBooks extends Component {
state = {
query: '',
results: []
}
updateQuery(query) {
this.setState(() => ({
results: [],
query: query
}))
this.bookSearch(query)
}
bookSearch(e) {
if (e.length > 0)
BooksAPI.search(e)
.then(searchResults => this.setState(currentState => ({
results: this.updateExistingShelves(searchResults)
})));
}
updateExistingShelves(searchResults) {
if(searchResults.error !== "empty query") {
const myBooks = this.props.books // books used here
const addToState = searchResults.filter((result) => myBooks.find(b => {
if(b.id === result.id)
result.shelf = b.shelf
return result
}))
myBooks.concat(addToState)
return searchResults
}
}

render() {
const { query, results } = this.state
const { onUpdateShelf, books, onUpdateBooksState } = this.props
return(
<div className="search-books">
<div className="search-books-bar">
<a className="close-search" >Close</a>
<div className="search-books-input-wrapper">
<input
type="text"
placeholder="Search by title, author or subject"
value={query}
onChange={(event) => this.updateQuery(event.target.value)}
/>
</div>
</div>
<div className="search-books-results">
<ol className="books-grid">
<li>
{ results ? (
results.map((book) => (
<Book
key={book.id}
book={book}
updateShelf={onUpdateShelf}  // onUpdateShelf used here
/>
))
) : (
<h4>No results for, "{query}"</h4>
)}
</li>
</ol>
</div>
</div>
)
}
}

编译器警告：

./src/SearchBooks.js Line 45: 'books' is assigned a value but never used no-unused-vars Line 45: 'onUpdateBooksState' is assigned a value but never used no-unused-vars

铬警告：

webpackHotDevClient.js:138 ./src/SearchBooks.js
Line 46:  'books' is assigned a value but never used               no-unused-vars
Line 46:  'onUpdateBooksState' is assigned a value but never used  no-unused-vars

Answer 1

它是一个 EsLint 警告，以防止您声明未使用的变量。

在此行中，您声明(不使用(变量

const { onUpdateShelf, books, onUpdateBooksState } = this.props

变量books和onUpdateBooksState不会在代码中的任何位置使用。

只需摆脱它们并将行更改为

const { onUpdateShelf } = this.props