[英]Why is React telling me that this.handleClick is not a function?
我正在使用 React 創建一個簡單的計算器,我正在嘗試將 onClick function 添加到按鈕。 我正在使用與 tictactoe 游戲的反應教程中使用的相同技術,但是當我單擊任何按鈕時,我只會收到以下錯誤消息:
Uncaught TypeError: this.handleClick is not a function
at onClick (index.js:71)
at HTMLUnknownElement.callCallback (react-dom.development.js:188)
at Object.invokeGuardedCallbackDev (react-dom.development.js:237)
at invokeGuardedCallback (react-dom.development.js:292)
at invokeGuardedCallbackAndCatchFirstError (react-dom.development.js:306)
at executeDispatch (react-dom.development.js:389)
at executeDispatchesInOrder (react-dom.development.js:414)
at executeDispatchesAndRelease (react-dom.development.js:3278)
at executeDispatchesAndReleaseTopLevel (react-dom.development.js:3287)
at forEachAccumulated (react-dom.development.js:3259)
at runEventsInBatch (react-dom.development.js:3304)
at runExtractedPluginEventsInBatch (react-dom.development.js:3514)
at handleTopLevel (react-dom.development.js:3558)
at batchedEventUpdates$1 (react-dom.development.js:21871)
at batchedEventUpdates (react-dom.development.js:795)
at dispatchEventForLegacyPluginEventSystem (react-dom.development.js:3568)
at attemptToDispatchEvent (react-dom.development.js:4267)
at dispatchEvent (react-dom.development.js:4189)
at unstable_runWithPriority (scheduler.development.js:653)
at runWithPriority$1 (react-dom.development.js:11039)
at discreteUpdates$1 (react-dom.development.js:21887)
at discreteUpdates (react-dom.development.js:806)
at dispatchDiscreteEvent (react-dom.development.js:4168)
我的代碼如下:
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
class Screen extends React.Component {
render() {
return (
<p>99+10</p>
);
}
}
class Operators extends React.Component {
render() {
return (
<div>
{this.props.renderButton('+')}
{this.props.renderButton('-')}
{this.props.renderButton('x')}
{this.props.renderButton('/')}
</div>
);
}
}
class Numbers extends React.Component {
render() {
return (
<div>
<div className="nums-row">
{this.props.renderButton(1)}
{this.props.renderButton(2)}
{this.props.renderButton(3)}
</div>
<div className="nums-row">
{this.props.renderButton(4)}
{this.props.renderButton(5)}
{this.props.renderButton(6)}
</div>
<div className="nums-row">
{this.props.renderButton(7)}
{this.props.renderButton(8)}
{this.props.renderButton(9)}
</div>
<div className="nums-row">
{this.props.renderButton('.')}
{this.props.renderButton(0)}
{this.props.renderButton('=')}
</div>
</div>
);
}
}
function CalculatorButton(props) {
return (
<button onClick={props.onClick} >
{props.text}
</button>
);
}
class Calculator extends React.Component {
handleClick(text) {
console.log(text);
}
renderButton(text) {
return (
<CalculatorButton
onClick= {() => this.handleClick(text)}
text={text}
/>
);
}
render() {
return (
<div className="calculator-container">
<div className="calculator">
<div className="screen">
<Screen />
</div>
<div className="buttons">
<div className="numbers">
<Numbers renderButton={this.renderButton} />
</div>
<div className="operators">
<Operators renderButton={this.renderButton} />
</div>
</div>
</div>
</div>
);
}
}
ReactDOM.render(
<Calculator />,
document.getElementById('root')
);
這是界面的圖片,這樣可能更容易理解我在問題開始時所說的內容。
提前感謝您的幫助。
您需要將renderButton
function 綁定到Calculator
組件實例。
這可以通過多種方式完成:
#1。 在構造函數中:
class Calculator extends React.Component {
constructor(props) {
super(props);
this.renderButton = this.renderButton.bind(this);
}
/* ... */
}
#2。 在渲染中:
<Numbers renderButton={this.renderButton.bind(this)} />
#3。 或者通過將renderButton
方法更改為箭頭 function:
renderButton = (text) => {
/* ... */
}
更多細節以及一些優點和缺點可以在React 常見問題解答部分找到。
this.props.renderButton('+')
立即調用renderButton
並將返回值分配為事件處理程序。
<button onClick={(e) => this.deleteRow(id, e)}>Delete Row</button> <button onClick={this.deleteRow.bind(this, id)}>Delete Row</button>
上面兩行是等價的,分別使用箭頭函數和Function.prototype.bind。
在這兩種情況下,表示 React 事件的 e 參數將作為 ID 之后的第二個參數傳遞。 使用箭頭 function,我們必須顯式傳遞它,但綁定任何進一步的 arguments 都會自動轉發。
要解決您的問題,只需使用 Arrow function。 為此,請將兩個事件處理程序handleClick 和 renderButton替換為以下代碼。 它完美地工作。
handleClick = (text) => {
console.log(text);
};
renderButton = (text) => {
return (
<CalculatorButton
onClick={() => this.handleClick(text)}
text={text}
/>
);
};
您還可以將 onclick 設置為 null,認為 <ComboSelect... onClick={null} /> 對我來說是正確的
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