reactjs - React + Firebase 使用钩子(Hook)？

Question

我找到了一个很棒的教程，介绍如何将 React 与 Firebase 结合使用，非常简单，只需将文本字段的数据存储在数据库中，但我对如何将其转换为使用 Hooks 感到困惑。我在那里找不到很多关于使用 Hooks + Firebase 的教程，所以我很感激任何帮助!

import React, {useState} from 'react'
import fire from './fire'
import './App.css'

const App = () => {
  let [messageList, setMessageList] = useState([])

  const handleSubmit = (e) => {
    e.preventDefault()
  }

  return(
    <section>
    <form onSubmit={handleSubmit}>
      <input type="text"></input>
      <button>Test</button>
    </form>
    <span>Messages: {messageList}</span>
    </section>
  )
}

class ThisWorksButNotWithHooks extends React.Component {
  constructor(props) {
    super(props);
    this.state = { messages: [] }; // <- set up react state
  }
  componentWillMount(){
    /* Create reference to messages in Firebase Database */
    let messagesRef = fire.database().ref('messages').orderByKey().limitToLast(100);
    messagesRef.on('child_added', snapshot => {
      /* Update React state when message is added at Firebase Database */
      let message = { text: snapshot.val(), id: snapshot.key };
      this.setState({ messages: [message].concat(this.state.messages) });
    })
  }
  addMessage(e){
    e.preventDefault(); // <- prevent form submit from reloading the page
    /* Send the message to Firebase */
    fire.database().ref('messages').push( this.inputEl.value );
    this.inputEl.value = ''; // <- clear the input
  }
  render() {
    return (
      <form onSubmit={this.addMessage.bind(this)}>
        <input type="text" ref={ el => this.inputEl = el }/>
        <input type="submit"/>
        <ul>
          { /* Render the list of messages */
            this.state.messages.map( message => <li key={message.id}>{message.text}</li> )
          }
        </ul>
      </form>
    );
  }
}

export default App;

我知道它正在与 Firebase 正常通信，因为 ThisWorksButNotWithHooks 有效，感谢 https://www.codementor.io/yurio/all-you-need-is-react-firebase-4v7g9p4kf .我通过查看一个基本的简单示例并通过反复试验从那里开始学习，所以我学得最好，所以如果我知道如何使用 Hooks 做到这一点，我就可以学习更复杂的用法。

谢谢!

Answer 1

像这样的东西应该可以工作。我并没有真正关注您的 Firebase 逻辑或返回的 html，只是展示了如何使用 useEffect 和 useState Hook :

const App = () => {
  const [messageList, setMessageList] = useState([])
  const [inputEl, setInputEl] = React.useState(null)
  
  React.useEffect(() => {
    /* Create reference to messages in Firebase Database */
    let messagesRef = fire.database().ref('messages').orderByKey().limitToLast(100);

    // As you are using a listener, declare it so it can be returned
    const listener = messagesRef.on('child_added', snapshot => {

      // Below logic just adds to the current 'messages' state  
      const message = { text: snapshot.val(), id: snapshot.key };
      const updatedMessagesArray = [...messageList].push(message)
      setMessageList(updatedMessagesArray)
    })

    return () => listener() // <== the listener returns the unsubscribe function, which the hook will automatically run when the component unmounts.

  }, []) // <== run once onMount

  async function addMessage(e){
    e.preventDefault(); // <- prevent form submit from reloading the page
    /* Send the message to Firebase */
    await fire.database().ref('messages').push( inputEl.value );
    setInputEl(null)
  }
  
  const handleSubmit = (e) => {
    e.preventDefault()
  }

 return(
    <section>
    <form onSubmit={handleSubmit}>
      <input type="text"></input>
      <button>Test</button>
    </form>
    <span>Messages: {messageList}</span>
    </section>
  )
  
}

将一个空数组作为第二个参数传递给 useEffect 钩子(Hook)将告诉它只在组件挂载时运行一次，返回监听器将使钩子(Hook)在组件卸载时取消订阅监听器。