javascript - redux mapDispatchToProps 不更新状态

Question

我是 redux 新手，遇到了 mapDispatchToProps 的问题， 我的 React 应用程序中有一个具有不同 div 的组件，每次用户单击 div 时，它都应该通过参数更改所选颜色，然后将其作为 prop 再次传递。

我从初始状态获取 Prop ，但无法让 mapDispatchToProps 正常工作。 似乎有不同的方法来处理mapDispatchToProps，我尝试了一些但没有工作， 这就是我目前所拥有的，没有错误但仍然无法运行

组件:

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

const ColorPalette = ({ selectedColor, changeSelectedColor }) => {

    return(
        <div>
            <div className='flex justify-center mb-2'>
                <p>Selected color: {selectedColor}</p>
            </div>
            <div className='flex justify-center mb-2'>
                <button onClick={() => changeSelectedColor('test')} className='border border-black'>
                   click to change
                </button>
            </div>
        </div>
    )
}

const mapStateToProps = (state) => {
    return { 
        selectedColor: state.colorReducer.selectedColor, 
    }
}

const mapDispatchToProps = (dispatch) => {
    return {
        changeSelectedColor: (color) => dispatch(changeSelectedColor(color))    
    }
}

export default connect(mapStateToProps, mapDispatchToProps)(ColorPalette);

reducer :

import { combineReducers } from "redux";

const initialState = {
  selectedColor: 'black',
};

const colorReducer = (state = initialState, action) => {
    switch(action.payload) {
        case 'SET_SELECTED_COLOR':
            console.log('changing color to ', action)
            return {...state, selectedColor: action.payload};
        default:
            return state;
    }       
}

export default combineReducers({
  colorReducer,
});

Action :

export const changeSelectedColor = (color) => {
    return {
        type: 'SET_SELECTED_COLOR',
        payload: color
    }
}

我还尝试将mapDispatchToProps作为对象传递，在这种情况下，如果我理解正确的话，每个函数都应该自动用dispatch包装？并且不向 connect 传递第二个参数，并将调度作为 Prop ，直接在单击时调度操作， 但就像我说的，两种方法都失败了

Answer 1

问题来自于您的 reducer :

const colorReducer = (state = initialState, action) => {
    switch(action.type) { // <== here should be type not payload
        case 'SET_SELECTED_COLOR':
            console.log('changing color to ', action)
            return {...state, selectedColor: action.payload};
        default:
            return state;
    }       
}

---

建议(与答案无关)

编写如下连接函数:

const mapStateToProps = ({ colorReducer: { selectedColor } = {} }) => ({ 
  selectedColor, 
});

const mapDispatchToProps = dispatch => ({
  changeSelectedColor: color => dispatch(changeSelectedColor(color)),
});

还有你的 Action 和 reducer :

export const changeSelectedColor = payload => ({
  type: 'SET_SELECTED_COLOR',
  payload,
});

const colorReducer = (state = initialState, { type, payload }) => {
  switch (type) {
    case 'SET_SELECTED_COLOR':
      return { ...state, selectedColor: payload };
    default:
      return state;
  }
};

在ReactJS中使用重组赋值，它很常见，可以让你的代码更具可读性和更好的调试性。