本文介绍了在 React 中将函数传递给子组件的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我正在尝试将一个函数传递给 React 中的子组件.如果我将函数放在 ES6 类中,我可以访问 this.props.dispatch,但在 mapStateToProps

中没有访问权限

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

有人可以识别我在访问 this.props.dispatch 以及在 mapStateToProps 函数中可用的函数的错误

import React, { Component } from 'react';从'react-redux'导入{连接};从'../denomInput/DenomInput.js'导入DenomInput;从'../../actions/countActions'导入*作为动作;类 CountableItems 扩展组件 {构造函数(道具){超级(道具);this.onDenomChange = this.onDenomChange.bind(this);}onDenomChange = (value, denom) =>{this.props.dispatch(actions.increaseSum(value, denom));控制台日志(值);}使成为() {const props = this.props;让 denomGroups = props.denoms.map(function (denom, i) {返回 (Object.keys(denom).map(function (key) {让 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>)}));});返回 (<div className="countable-item-wrapper"><div className="row">{denomGroups}

);}}函数 mapStateToProps(state, ownProps) {返回 {denoms: state.count.denomGroups,onDenomChange: this.onDenomChange}}导出默认连接(mapStateToProps)(CountableItems);

这里是渲染

的组件

import React, { Component } from 'react';从 '../components/countableItems/CountableItems.js' 导入 CountableItems;从 '../components/countSummary/CountSummary.js' 导入 CountSummary;导入./Count.css";类计数扩展组件{使成为() {返回 (<div className="容器"><div className="row"><div className="col-8"><CountableItems/>

<div className="col-4"><CountSummary/>

);}}

导出默认计数;

解决方案

您想传递对 CountableItems 实例的 onDenomChange 属性的引用.你可以通过像 onDenomChange={this.onDenomChange} 一样引用 this.onDenomChange 来做到这一点.

重要提示:你需要使用箭头函数() =>{} 以便 this 引用嵌套循环内的 CountableItems 实例.像 function () {} 这样的常规函数​​不会使用正确的上下文.

import React, { Component } from 'react';从'react-redux'导入{连接};从'../denomInput/DenomInput.js'导入DenomInput;从'../../actions/countActions'导入*作为动作;类 CountableItems 扩展组件 {onDenomChange = (value, denom) =>{this.props.dispatch(actions.increaseSum(value, denom));控制台日志(值);}使成为() {让 denomGroups = this.props.denoms.map((denom, i) => {返回 (Object.keys(denom).map((key) => {让 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>)}));});返回 (<div className="countable-item-wrapper"><div className="row">{denomGroups}

);}}函数 mapStateToProps(state, ownProps) {返回 {denoms: state.count.denomGroups,}}导出默认连接(mapStateToProps)(CountableItems);

I am trying to pass a function down to a child component in React. If I place the function within the ES6 class I have access to this.props.dispatch, but do not have access within mapStateToProps

Conversely when I define the function outside of the ES6 class I seem to have access to the function but not this.props.dispatch

Can someone identify what I am doing wrong to have both access to this.props.dispatch as well as having the function available in mapStateToProps function

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);

Here is the component that renders <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>
    );
  }
}

export default Count;

解决方案

You want to pass a reference to the CountableItems instance's onDenomChange property. You can do that by referencing this.onDenomChange like onDenomChange={this.onDenomChange}.

Important note: you need to use arrow functions () => {} in order for for this to reference the CountableItems instance inside your nested loops. Regular functions like function () {} would not use the correct context.

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);

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08-13 11:14