Question

我正在尝试使用对Codepen做出反应的单个问题测验应用程序。我正在使用api来获取问题，3个错误答案和对该问题的正确答案，并将其添加到状态中。验证答案时出现问题。单击4个选项之一后，我想有条件地渲染一个div。但是问题在于，在显示结果之后，将呈现另一个单选输入。

const appRoot = document.getElementById('app');

class App extends React.Component{
  state={
    question:'',
    correct:'',
    incorrect:[],
    result: null
  }

componentDidMount(){
  axios.get('https://opentdb.com/api.php?amount=1&type=multiple')
  .then(res => {
    const data = res.data.results[0];
    const q = data.question;
    const correct = data.correct_answer;
    const incorrect = data.incorrect_answers;
    this.setState({question:q,correct:correct,incorrect:incorrect})
  })
}

evaluate(selected){
  if(selected === this.state.correct){
    this.setState({result: 'Correct!'})
  } else {
    this.setState({result:`Wrong! Correct Answer is ${this.state.correct}`})
  }
}

render(){
  const random = Math.floor(Math.random() * 3);
  const options = this.state.incorrect;
  options.splice(random, 0, this.state.correct);
  const choices = options.map((option,i) => (
    <div>
      <input type='radio' 
     name='option' 
     value={option} 
     key={i} onChange={() => this.evaluate(option)}/>
      <label for='option'>{option}</label>
    </div>
  ) )
  return(
    <div>
      <div>{this.state.question}</div>
      <div>{choices}</div>
      <div>{this.state.result}</div>
    </div>
  )
}
}

ReactDOM.render(<App />, appRoot)

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<div id='app'></div>

Answer 1

这似乎是一个诚实的错误（我一贯有罪）：

在您的render方法中，您可以对数组进行突变：

const options = this.state.incorrect;
options.splice(random, 0, this.state.correct);

我怀疑您想要的是什么

const options = this.state.incorrect.slice(); //create a COPY of the array
options.splice(random, 0, this.state.correct);

React基本上是一种状态机，用于查找状态更改并智能地更新依赖于该状态的零件。但这只是JavaScript。通过直接拼接状态对象，您可以在render方法中更改状态。 React不知道您更改了状态，因此，您最终会遇到意想不到的行为，尤其是render经常被调用。

我已经复制了您的代码段，以便您可以看到一个有效的示例。

const appRoot = document.getElementById('app');

class App extends React.Component{
  state={
    question:'',
    correct:'',
    incorrect:[],
    result: null
  }

componentDidMount(){
  axios.get('https://opentdb.com/api.php?amount=1&type=multiple')
  .then(res => {
    const data = res.data.results[0];
    const q = data.question;
    const correct = data.correct_answer;
    const incorrect = data.incorrect_answers;
    this.setState({question:q,correct:correct,incorrect:incorrect})
  })
}

evaluate(selected){
  if(selected === this.state.correct){
    this.setState({result: 'Correct!'})
  } else {
    this.setState({result:`Wrong! Correct Answer is ${this.state.correct}`})
  }
}

render(){
  const random = Math.floor(Math.random() * 3);
  const options = this.state.incorrect.slice();
  options.splice(random, 0, this.state.correct);
  const choices = options.map((option,i) => (
    <div>
      <input type='radio' 
     name='option' 
     value={option} 
     key={i} onChange={() => this.evaluate(option)}/>
      <label for='option'>{option}</label>
    </div>
  ) )
  return(
    <div>
      <div>{this.state.question}</div>
      <div>{choices}</div>
      <div>{this.state.result}</div>
    </div>
  )
}
}

ReactDOM.render(<App />, appRoot)

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<div id='app'></div>

选择时重复的无线电输入（反应）

1 个答案: