Question

    

    
       I am new to React and trying to understand the basics. I have a child component called movieList that return a list of movies in a table form. 
    const movieList = () =>{ 
        const {movies} = props;
        return (){
        <tbody>
          <Fragment>
            {movies.map((movie, i) => (
            <tr key={i}>
              <td>{movie.title}</td>
              <td>{movie.genre.name}</td>
              <td>{movie.numberInStock}</td>
              <td>{movie.dailyRentalRate}</td>
              <td><button className="btn btn-danger btn-sm" onClick={props.onClick} movie={props.movie}>Delete</button></td>
    
            </tr>
            ))}
    
          </Fragment>
        </tbody>
        } }
    
    



  And the Parent

    
       I am new to React and trying to understand the basics. I have a child component called movieList that return a list of movies in a table form. 
    const movieList = () =>{ 
        const {movies} = props;
        return (){
        <tbody>
          <Fragment>
            {movies.map((movie, i) => (
            <tr key={i}>
              <td>{movie.title}</td>
              <td>{movie.genre.name}</td>
              <td>{movie.numberInStock}</td>
              <td>{movie.dailyRentalRate}</td>
              <td><button className="btn btn-danger btn-sm" onClick={props.onClick} movie={props.movie}>Delete</button></td>
    
            </tr>
            ))}
    
          </Fragment>
        </tbody>
        } }

我在桌子上正确地获得了电影列表。但是我想将按钮定位为单击按钮时删除。我知道我需要通过子组件movieList中的道具传递电影，但是我似乎无法弄清楚如何通过电影才能删除它。通过onClick属性上调用的handleDelete函数，我在控制台上得到了一个未定义的值。而我希望在单击时能获得电影的价值。我该如何在React中做到这一点。

Answer 1

很酷，所以您有电影列表，只需要删除正确的电影即可。我们将尝试通过数组中的索引删除该电影。我们将使用array.filter()方法。请参阅沙箱以供参考：https://codesandbox.io/s/intelligent-dan-uskcy

父母

class Movies extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      movies: [
        { genre: { name: "Avengers: End Game" }, numberInStock: 100000, dailyRentalRate: 1 },
        { genre: { name: "Harry Potter" }, numberInStock: 20000, dailyRentalRate: 2 },
        { genre: { name: "DBZ" }, numberInStock: 200000, dailyRentalRate: 1}
      ]
    }; // assuming movies is an array
  }

  handleDelete = movieIndex => {
    const { movies } = this.state;
    const updatedMovies = movies.filter((movie, index) => {
      return index !== movieIndex;
    });

    this.setState({
      movies: updatedMovies
    });
  };

  render() {
    return (
      <MovieList movies={this.state.movies} handleDelete={this.handleDelete} />
    );
  }
}

因此handleDelete()以索引作为参数，我们用它来创建新的电影数组，其中不包含带有传入索引的电影。

然后在.map()组件的MovieList中，我们还将使用可用的index参数，并将该索引传递到事件处理程序props.handleDelete(i)中。这将调用父组件中定义的handleDelete()函数，并将更新状态。

孩子

const MovieList = (props) =>{ 
  const {movies} = props;
  return (
    <tbody>
    <Fragment>
      {movies.map((movie, i) => (
      <tr key={i}>
         <td>{movie}</td>
         <td>{movie.genre.name}</td>
         <td>{movie.numberInStock}</td>
         <td>{movie.dailyRentalRate}</td>
         <td><button className="btn btn-danger btn-sm" onClick={() => props.handleDelete(i)} movie={props.movie}>Delete</button></td>
          </tr>
       ))}
     </Fragment>
   </tbody>
  )
}

Answer 2

您需要通过回调传递movie元素。将您的子组件onlick更改为：

onClick={() => props.onClick(movie)}

然后，您需要将数据从回调传递到父级函数中

onClick={movie => this.handleDelete(movie)}

或者只是

onClick={this.handleDelete}

然后您要做的就是从您所在州的列表中删除该电影。然后，React将从DOM中删除该元素：

handleDelete = (movie) => {
   const { movies } = this.state;
   const newMoviews = movies.slice();
   newMovies.splice(newMovies.findIndex(m => m.title === movie.title), 1)
   this.setState({ movies: newMovies });
}

将清单孩子传递给父母

2 个答案:

父母

孩子