Question

我是新来反应钩子的人，我很难转换此类，使用ES6语法编写React钩子。可以请帮助我。这是我的信条...

import React, { Component } from 'react';
import { connect } from 'react-redux';
import { Link } from 'react-router-dom';

import { fetchMovie, setLoading } from '../../actions/searchActions';

import Spinner from '../layout/Spinner';

export class Movie extends Component {
  componentDidMount() {
    this.props.fetchMovie(this.props.match.params.id);
    this.props.setLoading();
  }
  render() {
    const { loading, movie } = this.props;

    let movieInfo = (
      <div className="container">
       jsx......
 </div>
    );

    let content = loading ? <Spinner /> : movieInfo;
    return <div>{content}</div>;
  }
}

const mapStateToProps = state => ({
  loading: state.movies.loading,
  movie: state.movies.movie
});

export default connect(
  mapStateToProps,
  { fetchMovie, setLoading }
)(Movie);

Answer 1

一些最常用的钩子是useState，useEffect。 useState在某些方面类似于setState，区别之一是您没有useState的回调功能。您可以使用useEffect实现类似的效果。 useEffect可以用作componentDidMount，componentDidUpdate和componentWillUnmount。如果传递一组空的依存关系[]（如以下示例所示），则其行为与componentDidMount相同。如果您希望基于某些条件（例如，正在更新的状态）来触发特定功能，则可以将其作为dependancy传递。然后，useEffect表现为componentDidUpdate。 useEffect接受第三个参数作为回调函数。在卸载组件时触发此操作，从而增加了componentWillUnmount行为。

import React, { useEffect } from 'react';
import { connect } from 'react-redux';
import { Link } from 'react-router-dom';

import { fetchMovie, setLoading } from '../../actions/searchActions';

import Spinner from '../layout/Spinner';

const Movie = () => {
  useEffect(() => {
    props.fetchMovie(props.match.params.id);
    props.setLoading();
  }, [])
  const { loading, movie } = props;

    let movieInfo = (
      <div className="container">
       jsx......
      </div>
    );

  let content = loading ? <Spinner /> : movieInfo;
  return <div>{content}</div>;
}

const mapStateToProps = state => ({
  loading: state.movies.loading,
  movie: state.movies.movie
});

export default connect(
  mapStateToProps,
  { fetchMovie, setLoading }
)(Movie);

Answer 2

您可以像这样重写钩子。

import React, { useEffect } from 'react';
import { useDispatch, useSelector } from 'react-redux';
import { Link } from 'react-router-dom';

import { fetchMovie, setLoading } from '../../actions/searchActions';

import Spinner from '../layout/Spinner';

export const Movie = ({ match}) => {
  const dispatch = useDispatch();
  const movie = useSelector(state => state.movies.movie);
  const loading = useSelector(state => state.movies.loading);
  useEffect(() => {
        dispatch(fetchMovie(match.params.id));
        dispatch(setLoading());
     }, []);

  return (
    <div>
      {
        loading 
         ? <Spinner /> 
         : <div className="container">
            jsx......
          </div>
      }
    </div>
  )
}

使用空数组作为参数的

useEffect类似于componentDidMount。然后我将连接更改为useSelector和useDispatch

将React中的类基础组件转换为钩子

2 个答案: