[英]How can I return the numeric value of a React container instead of an object?
我正在尝试学习 React,并且正在开发一个简单的 web 应用程序来实现我迄今为止在网上学到的东西。
我有一个名为CardDatabase.js
的容器,它返回的只是一个值。 这个值称为reduceArray
,它是一个调用了reduce()
方法的数组。 当我渲染<CardDatabase.js />
时,值会按预期出现在浏览器和控制台中(在屏幕截图中,它是 86)。 但是,当我尝试将<CardDatabase />
的值分配给App.js
中的calculate
方法内的变量w
时,会返回 object 而不是数值(检查屏幕截图中的控制台)。
如何将<CardDatabase />
的数值分配给变量,以便我可以使用它来计算一些简单的数学?
我也尝试使用 props 和this.state
但是根据我得到的控制台错误和 React 文档,我们不能修改 props 的值? 所以当我尝试类似的事情时:
const array = (rarityOfArray) => {
filteredArray = rarityOfArray.filter(item => item.key <= level)
for(let x = 0; x < filteredArray.length; x++) {
pushedArray.push(filteredArray[x].cardsRequiredToUpgrade)
console.log(pushedArray);
}
props.array = pushedArray.reduce((a, b) => a + b, 0);
console.log("Reduced - " + reducedArray);
return props.array
}
我收到此错误消息: TypeError: Cannot assign to read only property 'array' of object '#<Object>'
任何帮助或方向将不胜感激。
应用程序.js
import React, {Component} from 'react';
// CSS
import 'bootstrap/dist/css/bootstrap.min.css';
import './App.css';
// Components
import CardRarityDropdown from './components/CardRarityDropdown';
import CardLevelDropdown from './components/CardLevelDropdown';
import CardAmountInput from './components/CardAmountInput';
import CardCalculationsButton from './components/CardCalculationsButton';
//Containers
import CardDatabase from './containers/cardDatabase/CardDatabase';
class App extends Component {
constructor() {
super();
this.state = {
cardRarity: "",
cardLevel: "",
amountOfCards: "",
}
this.setCardValues = this.setCardValues.bind(this);
}
setCardValues = (event) => {
const {name, value} = event.target
this.setState({
[name]: value
})
}
calculate = () => {
let v = this.state.cardRarity;
console.log("v: " + v)
let w = <CardDatabase />
console.log("w: " + w)
let x = v - w;
console.log("x: " + x)
let y = this.state.amountOfCards;
console.log("y: " + y)
let z = x - y;
console.log("z: " + z)
return z
}
render () {
return (
<div>
<h1 id="superCellText">Clash Royale Card Calculator</h1>
<CardRarityDropdown
setCardValues={this.setCardValues}
cardRarity={this.state.cardRarity} />
<CardLevelDropdown
setCardValues={this.setCardValues}
cardRarity={this.state.cardRarity}
cardLevel={this.state.cardLevel} />
<CardDatabase
cardRarity={this.state.cardRarity}
cardLevel={this.state.cardLevel} />
<CardAmountInput
setCardValues={this.setCardValues}
cardRarity={this.state.cardRarity}
amountOfCards={this.state.amountOfCards} />
<CardCalculationsButton
calculate={this.calculate}
cardRarity={this.state.cardRarity} />
</div>
);
}
}
export default App;
CardDatabase.js
import common from './Common';
import rare from './Rare';
import epic from './Epic';
import legendary from './Legendary';
const CardDatabase = (props) => {
const card = props.cardRarity;
const level = props.cardLevel;
let filteredArray = [];
let pushedArray = [];
let reducedArray = [];
const array = (rarityOfArray) => {
filteredArray = rarityOfArray.filter(item => item.key <= level)
for(let x = 0; x < filteredArray.length; x++) {
pushedArray.push(filteredArray[x].cardsRequiredToUpgrade)
console.log(pushedArray);
}
reducedArray = pushedArray.reduce((a, b) => a + b, 0);
console.log("Reduced - " + reducedArray);
return reducedArray
}
if(card === "9586") {return array(common)}
if(card === "2586") {return array(rare)}
if(card === "386") {return array(epic)}
if(card === "36") {return array(legendary)}
if(card === "") {return null}
}
export default CardDatabase;
Reddit 和 Discord 上的人们给了我相同的反馈,如果该组件没有返回任何与 UI 相关的内容,我不应该使用该组件。 因此, CardDatabase.js
不应该是一个组件,而是一个简单的 function。
我将其名称更改为cardDatabase.js
,以便 React 不再将其视为组件,而不是接收道具,function 现在具有标准参数。
更新了 cardDatabase.js
import common from './Common';
import rare from './Rare';
import epic from './Epic';
import legendary from './Legendary';
const cardDatabase = (cardRarity, cardLevel) => {
let filteredArray = [];
let pushedArray = [];
let reducedArray = [];
const array = (rarityOfArray) => {
filteredArray = rarityOfArray.filter(item => item.key <= cardLevel)
for(let x = 0; x < filteredArray.length; x++) {
pushedArray.push(filteredArray[x].cardsRequiredToUpgrade)
console.log(pushedArray);
}
reducedArray = pushedArray.reduce((a, b) => a + b, 0);
console.log("Reduced - " + reducedArray);
return reducedArray
}
if(cardRarity === "9586") {return array(common)}
if(cardRarity === "2586") {return array(rare)}
if(cardRarity === "386") {return array(epic)}
if(cardRarity === "36") {return array(legendary)}
if(cardRarity === "") {return null}
}
export default cardDatabase;
In App.js
I removed the <CardDatabase />
component and inside of my calculate
method, simply assigned the value of variable w
to my cardDatabase
function with this.state.cardRarity
and this.state.cardLevel
as the arguments.
更新了 App.js
import React, {Component} from 'react';
// CSS
import 'bootstrap/dist/css/bootstrap.min.css';
import './App.css';
// Components
import CardRarityDropdown from './components/CardRarityDropdown';
import CardLevelDropdown from './components/CardLevelDropdown';
import CardAmountInput from './components/CardAmountInput';
import CardCalculationsButton from './components/CardCalculationsButton';
//Containers
import cardDatabase from './containers/cardDatabase/cardDatabase.js';
class App extends Component {
constructor() {
super();
this.state = {
cardRarity: "",
cardLevel: "",
amountOfCards: "",
}
this.setCardValues = this.setCardValues.bind(this);
}
setCardValues = (event) => {
const {name, value} = event.target
this.setState({
[name]: value
})
}
calculate = () => {
let rarity = this.state.cardRarity;
let level = this.state.cardLevel;
console.log("v: " + rarity)
let w = cardDatabase(rarity, level);
console.log("w: " + w)
let x = rarity - w;
console.log("x: " + x)
let y = this.state.amountOfCards;
console.log("y: " + y)
let z = x - y;
console.log("z: " + z)
return z
}
render () {
return (
<div>
<h1 id="superCellText">Clash Royale Card Calculator</h1>
<CardRarityDropdown
setCardValues={this.setCardValues}
cardRarity={this.state.cardRarity} />
<CardLevelDropdown
setCardValues={this.setCardValues}
cardRarity={this.state.cardRarity}
cardLevel={this.state.cardLevel} />
<CardAmountInput
setCardValues={this.setCardValues}
cardRarity={this.state.cardRarity}
amountOfCards={this.state.amountOfCards} />
<CardCalculationsButton
calculate={this.calculate}
cardRarity={this.state.cardRarity} />
</div>
);
}
}
export default App;
现在w
返回一个数值而不是 object 并且我的应用程序终于可以正常运行了。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.