高性能 Context

一.背景

解决了 Context re-render 问题，实现更精细化的控制策略。

常用策略有：多层Context方案 、 组件memo化方案。

使用起来代码量较多，因此使用发布订阅模式手撕高性能Context，使用起来也较为方便。

二.使用说明

// Context Store (./store.ts)
import { Payload2Action, Provider2Hook } from '@novel/dragon-utils/lib/use-perf-context';
export interface IUserInfo {
  name: string;
  age: number;
}
export interface IPayload {
  SET_USER_INFO: Partial<IUserInfo>
}
// IAction = { type: 'SET_USER_INFO', payload: { name?: string; age?: number } }
export type IAction = Payload2Action<IPayload>;

export const initialState: IState = {
  userInfo: {
    name: "",
    age: 0
  },
};

export const globalReducer = (state: IState, action: IAction) => {
  switch (action.type) {
    case ActionType.SET_USER_INFO:
      return {
        ...state,
        userInfo: action.payload
      };
    default:
      return state;
  }
};
// usePerfContext<目标state集合的类型约束, dispatch的对象类型约束，目标属性名>(目标属性对象的属性名字符串)
// 使用类型推断和Provider2Hook工具泛型将hook与provider相关属性绑定
export const useUserContext = usePerfContext as Provider2Hook<IState, IAction>;

// Context Provider
import PerfContextProvider from '@novel/dragon-utils/lib/use-perf-context';
function App() {
  return (
    <PerfContextProvider state={initialState} reducer={globalReducer}>
        <Header />
      <YourComponents />
    </PerfContextProvider>
  );
}

// Context Consumer
import { useUserContext } from './store';

function Header() {
  // same as: const [userInfo, dispatch] = usePerfContext<IState, IAction, 'userInfo'>('userInfo')
  const [userInfo, dispatch] = useUserContext("userInfo");

  const { name, age } = userInfo || {};
  renderCount++;
  const addAge = () => {
    dispatch({
      type: ActionType.SET_USER_INFO,
      payload: { name: "阿吉", age: Number(age) + 1 }
    });
  };

  return (
    <div className={classPrefix}>
      <div>{classPrefix}</div>
      <div>用户名：{name}</div>
      <div>年龄：{age}</div>
      <button onClick={addAge}>年龄增长一岁</button>
      <div>renderCount: {renderCount}</div>
    </div>
  );
}

三.example

在线demo: https://codesandbox.io/s/void4-context-rerender--proxy-completed-emv5n0?file=/src/store/index.tsx