从connect（mapStateToProps）获取状态>未定义

Question

I am kind of struggling to get the state of book, when I log the props I get book: undefined.

Any tips?

import React from 'react';
import { connect } from 'react-redux';
import BookForm from './BookForm';

const EditBook = (props) => {
 console.log(props)
  return (
    <div>
      hello
    </div>
  );
};

const mapStateToProps = (state, props) => {
  return {
    book: state.books.find((book) => book.id === props.match.params.id)
  };
};

export default connect(mapStateToProps)(EditBook);

Rest of the project is on my Github: https://github.com/bananafreak/bookshelf

Answer 1

I've ran into issues with this before where === will fail because the types of book.id and props.match.params.id are different. The params values are always strings - maybe try parseInt(props.match.params.id) or == comparison (with type coercion).

Answer 2

I managed to found where was my mistake.

In the component BookListItem:

import React from 'react';
import { Link } from 'react-router-dom';

const BookListItem = ({ author, title, genre, text, id, pages }) => (
  <div>
    <Link to={`/edit/${id}`}><h2>{title}</h2></Link>
    <h3>by: {author}</h3>
    <p>{genre}</p>
    {pages > 0 && <p>{pages} pages</p>}
    <p>{text}</p>
    <p>-------------------------------</p>
  </div>
);

export default BookListItem;

Before the ${id} I had unfortunately colon { /edit/:${id} } so then book.id and props.match.params.id could not match

Answer 3

Update the Link in the BookListItem . You don't need the : before ${id} . The : is causing the problem.

<Link to={`/edit/${id}`}><h2>{title}</h2></Link>

In the EditBook component return the following

<BookForm {...props}></BookForm>

In the BookForm constructor set the state from props.book

this.state = { ...props.book }