在以下代码中,combineReducers不会将数据(状态,操作)传递给reducer.它会在下面生成错误.可能只是我犯的一个小错误.链接到JSFiddle：https://jsfiddle.net/bengrunfeld/1h0t59uf/
import React from 'react'
import { render } from 'react-dom'
import { combineReducers } from 'redux'
import { Constants } from './constants/constants'
const goal = (state = 0,action) => {
(action.type === Constants.ADD) ?
state + action.payload:
state
}
const target = (state = 0,action) => {
(action.type === Constants.REMOVE)?
state - action.payload:
state
}
const reducer = combineReducers({
goal,target
})
const state = 10
const newState = reducer(state,{
type: Constants.REMOVE,payload: 5
})
render(
错误信息
main.bundle.js:28054 Uncaught Error: Reducer "goal" returned undefined during initialization. If the state passed to the reducer is undefined,you must explicitly return the initial state. The initial state may not be undefined.
at http://localhost:3000/main.bundle.js:28054:13
at Array.forEach (native)
at assertReducerSanity (http://localhost:3000/main.bundle.js:28049:25)
at combineReducers (http://localhost:3000/main.bundle.js:28104:5)
at Object.最佳答案
const Constants = {
REMOVE: "REMOVE",ADD: "ADD"
}
const goal = (state = 5,action) => {
return (action.type === Constants.ADD) ?
state + action.payload:
state
}
const target = (state = 5,action) => {
return (action.type === Constants.REMOVE)?
state - action.payload:
state
}
const reducer = Redux.combineReducers({
goal,target
})
const state = {goal: 10,target:5}
const newState = reducer(state,payload: 5
})
console.log(newState);
ReactDOM.render(
