初学redux，报错Cannot read property 'map' of undefined

Question

import React from 'react';
import DifferentLabels from './DifferentLabels'

const DifferentLabelsDiv = ({ todos, toggleTodo }) => (
    <div>
        {todos.map(todo =>
            <DifferentLabels
                key={todo.id}
                {...todo}
            />
        )}
    </div>
)

class DifferentLabelsList extends React.Component {

    render(){
        return (
            <div className={'left_layout'}>
                <div>
                    展示不同标签
                </div>
                <DifferentLabelsDiv />
            </div>
        )
    }
}

export default DifferentLabelsList;

import React from 'react'
import PropTypes from 'prop-types'

const DifferentLabels = ({ onClick, completed, text }) => (
    <div
    >
        {text}
    </div>
);

export default DifferentLabels

Answer 1

const DifferentLabelsDiv = ({ todos = [], toggleTodo }) ...

改成这样

Answer 2

你的DifferentLabelsDiv 组件有一个todos的属性，但是你并没有给这个组件传递这个属性，所以todos是undefined，所以你调用map方法会报错，
解决方法：

1. 传递todos属性
2. 给DifferentLabelsDiv这个组件一个默认的todos属性。