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react使用ctx和reducer代替redux

news 2025/9/24 16:08:45

入门版本

创建一个store，包含ctx、reduce、dispatch+action

import { createContext, useContext } from 'react';// 定义ctx
export const defaultValue = {count: 0,
};
export const AppCtx = createContext(null);export function useAppCtx() {const ctx = useContext(AppCtx);return ctx;
}// 定义reducer
export function appReducer(app, action) {switch (action.type) {case 'update': {return { ...app, ...action.payload };}case 'clear': {return {};}default: {throw Error('Unknown action: ' + action.type);}}
}// 定义dispatch和action（省的在组件手写dispatch）
export const appCtxDispatch = {update: (dispatch, payload) => {dispatch({type: 'update',payload,});},clear: (dispatch) => {dispatch({type: 'clear',})},
};

最后我们在组件中使用

import { memo, useReducer } from 'react';
import { AppCtx, appReducer, defaultValue, useAppCtx, appCtxDispatch } from '@/hooks/useAppCtx';// 子组件
const Demo = memo(() => {console.log('Demo render');const { app } = useAppCtx();return (<div>我是子组件<div>{JSON.stringify(app)}</div></div>);
});// 父组件
const App = () => {console.log('App render');const [app, dispatch] = useReducer(appReducer, defaultValue);const doInc = () => {appCtxDispatch.update(dispatch, {count: app.count + 1,});};return (<AppCtx value={app}><div>{app.count}</div><button onClick={doInc} className="bg-blue-400 p-1 rounded text-white">改变组件</button><hr className="mt-2" /><Demo /></AppCtx>);
};

优化版本

解决无辜组件的不必要的重新render问题

// app-store.ts
import { produce } from 'immer';
import { createContext, useContext } from 'react';// 定义ctx
export const defaultValue = {count: 0,
};
export const AppCtx = createContext(null);export function useAppCtx() {const ctx = useContext(AppCtx);return ctx;
}// 定义reducer
// 优化1: 使用immer，防止payload内容不变，而返回全新的对象导致 使用的地方被rerender
export function appReducer(app, action) {return produce(app, (draft) => {switch (action.type) {case 'update': {Object.assign(draft, action.payload); // 只真正改动的字段会触发草稿变更return; // 没改动时 Immer 自动返回旧引用}case 'clear': {return {};}default:throw new Error('Unknown action: ' + action.type);}});
}// 定义dispatch和action（省的在组件手写dispatch）
export const appCtxDispatch = {update: (dispatch, payload) => {dispatch({type: 'update',payload,});},clear: (dispatch) => {dispatch({type: 'clear',});},
};

组件中使用

import { memo, useMemo, useReducer } from 'react';
import { AppCtx, appReducer, defaultValue, useAppCtx, appCtxDispatch } from '@/hooks/useAppCtx';// 子组件
const Demo = memo(() => {console.log('Demo render');const { app } = useAppCtx();return (<div>我是子组件<div>{JSON.stringify(app)}</div></div>);
});// 父组件
const App = () => {console.log('App render');const [app, dispatch] = useReducer(appReducer, defaultValue);const doInc = () => {appCtxDispatch.update(dispatch, {count: app.count+1,});};// 优化2: 防止App本身render，导致ctx的值被迫改变const appCtxValue = useMemo(() => ({ app, dispatch }), [app]); return (<AppCtx value={appCtxValue}><div>{app.count}</div><button onClick={doInc} className="bg-blue-400 p-1 rounded text-white">改变组件</button><hr className="mt-2" /><Demo /></AppCtx>);
};