Question

我正在用React创建一个简单的计算器，并且试图向按钮添加onClick函数。我使用tictactoe游戏的react教程中使用了相同的技术，但是当我单击任何按钮时，我只会收到以下错误消息：

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)

我的代码如下：

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')
);

这是界面的图片，因此可能更容易理解我在问题开始时所说的话。

预先感谢您的帮助。

Answer 1

您需要将renderButton函数绑定到Calculator组件实例。

这可以通过几种方式完成：

＃1。在构造函数中：

class Calculator extends React.Component {
  constructor(props) {
    super(props);
    this.renderButton = this.renderButton.bind(this);
  }

  /* ... */
}

渲染中的

＃2。：

<Numbers renderButton={this.renderButton.bind(this)} />

＃3。或通过将renderButton方法更改为箭头功能：

renderButton = (text) => {
  /* ... */
}

更多详细信息以及一些优缺点可在React faq section on functions中找到。

Answer 2

this.props.renderButton('+')调用renderButton，立即，并将返回值分配为事件处理程序。

这是specifically covered in the React documentation：

<button onClick={(e) => this.deleteRow(id, e)}>Delete Row</button>
<button onClick={this.deleteRow.bind(this, id)}>Delete Row</button>
以上两行是等效的，并使用箭头功能和分别是Function.prototype.bind。

在两种情况下，代表React事件的e参数将是作为ID后的第二个参数传递。通过箭头功能，我们必须显式地传递它，但是使用bind绑定任何其他参数自动转发。

Answer 3

要解决您的问题，只需使用箭头功能。为此，请使用以下代码替换两个事件处理程序 handleClick和renderButton 。效果很好。

handleClick = (text) => {
    console.log(text);
};

renderButton = (text) => {
    return (
        <CalculatorButton
            onClick={() => this.handleClick(text)}
            text={text}
        />
    );
};

为什么React告诉我this.handleClick不是函数？

3 个答案: