在 React 中将函数向下传递给子组件

我试图将一个函数传递给 React 中的子组件。如果我将该函数放在 ES6 类中，我就可以访问this.props.dispatch，但无权访问mapStateToProps

相反，当我在 ES6 类之外定义函数时，我似乎可以访问该函数，但不能this.props.dispatch

有人可以找出我做错了什么才能同时访问this.props.dispatch以及具有可用的功能mapStateToProps功能

import React, { Component } from 'react';
import { connect } from 'react-redux';
import DenomInput from '../denomInput/DenomInput.js';
import * as actions from '../../actions/countActions';

class CountableItems extends Component {
  constructor(props) {
    super(props);
    this.onDenomChange = this.onDenomChange.bind(this);
  }

  onDenomChange = (value, denom) => {
    this.props.dispatch(actions.increaseSum(value, denom));
    console.log(value);
  }

  render() {
    const props = this.props;

    let denomGroups = props.denoms.map(function (denom, i) {
      return (
        Object.keys(denom).map(function (key) {
          let denoms = denom[key].map(function (item, i) {
            return <DenomInput denom={item} onDenomChange={props.onDenomChange} key={i}></DenomInput>
          });
          return (<div className="col"><h2>{key}</h2>{denoms}</div>)
        })
      );
    });

    return (
      <div className="countable-item-wrapper">
        <div className="row">
          {denomGroups}
        </div>
      </div>
    );
  }
}

function mapStateToProps(state, ownProps) {
  return {
    denoms: state.count.denomGroups,
    onDenomChange: this.onDenomChange
  }
}

export default connect(mapStateToProps)(CountableItems);

这是渲染的组件<CountableItems>

import React, { Component } from 'react';
import CountableItems from '../components/countableItems/CountableItems.js';
import CountSummary from '../components/countSummary/CountSummary.js';

import "./Count.css";

class Count extends Component {
  render() {
    return (
      <div className="container">
        <div className="row">
          <div className="col-8">
            <CountableItems />
          </div>
          <div className="col-4">
            <CountSummary />
          </div>
        </div>
      </div>
    );
  }
}

导出默认计数；

您想要传递对CountableItems实例的onDenomChange财产。您可以通过引用来做到这一点this.onDenomChange like onDenomChange={this.onDenomChange}.

重要提示：您需要使用箭头函数() => {}为了为了this来参考CountableItems嵌套循环内的实例。常规函数如function () {}不会使用正确的上下文。

import React, { Component } from 'react';
import { connect } from 'react-redux';
import DenomInput from '../denomInput/DenomInput.js';
import * as actions from '../../actions/countActions';

class CountableItems extends Component {
  onDenomChange = (value, denom) => {
    this.props.dispatch(actions.increaseSum(value, denom));
    console.log(value);
  }

  render() {
    let denomGroups = this.props.denoms.map((denom, i) => {
      return (
        Object.keys(denom).map((key) => {
          let denoms = denom[key].map((item, i) => {
            return <DenomInput denom={item} onDenomChange={this.onDenomChange} key={i}></DenomInput>
          });
          return (<div className="col"><h2>{key}</h2>{denoms}</div>)
        })
      );
    });

    return (
      <div className="countable-item-wrapper">
        <div className="row">
          {denomGroups}
        </div>
      </div>
    );
  }
}

function mapStateToProps(state, ownProps) {
  return {
    denoms: state.count.denomGroups,
  }
}

export default connect(mapStateToProps)(CountableItems);