我在我的React应用中使用带有hooks的React context作为状态管理器。每次存储中的值发生更改时,所有组件都会重新渲染。
有没有办法防止React组件重新渲染?
存储配置:
import React, { useReducer } from "react";
import rootReducer from "./reducers/rootReducer";
export const ApiContext = React.createContext();
export const Provider = ({ children }) => {
const [state, dispatch] = useReducer(rootReducer, {});
return (
<ApiContext.Provider value={{ ...state, dispatch }}>
{children}
</ApiContext.Provider>
);
};
一个 reducer 示例:
import * as types from "./../actionTypes";
const initialState = {
fetchedBooks: null
};
const bookReducer = (state = initialState, action) => {
switch (action.type) {
case types.GET_BOOKS:
return { ...state, fetchedBooks: action.payload };
default:
return state;
}
};
export default bookReducer;
根Reducer,可以组合尽可能多的Reducer:
import userReducer from "./userReducer";
import bookReducer from "./bookReducer";
const rootReducer = ({ users, books }, action) => ({
users: userReducer(users, action),
books: bookReducer(books, action)
});
一个行动的例子:
import * as types from "../actionTypes";
export const getBooks = async dispatch => {
const response = await fetch("https://jsonplaceholder.typicode.com/todos/1", {
method: "GET"
});
const payload = await response.json();
dispatch({
type: types.GET_BOOKS,
payload
});
};
export default rootReducer;
这是书籍组件:
import React, { useContext, useEffect } from "react";
import { ApiContext } from "../../store/StoreProvider";
import { getBooks } from "../../store/actions/bookActions";
const Books = () => {
const { dispatch, books } = useContext(ApiContext);
const contextValue = useContext(ApiContext);
useEffect(() => {
setTimeout(() => {
getBooks(dispatch);
}, 1000);
}, [dispatch]);
console.log(contextValue);
return (
<ApiContext.Consumer>
{value =>
value.books ? (
<div>
{value.books &&
value.books.fetchedBooks &&
value.books.fetchedBooks.title}
</div>
) : (
<div>Loading...</div>
)
}
</ApiContext.Consumer>
);
};
export default Books;
当 Books 组件中的值发生变化时,另一个名为 Users 的组件将重新渲染:
import React, { useContext, useEffect } from "react";
import { ApiContext } from "../../store/StoreProvider";
import { getUsers } from "../../store/actions/userActions";
const Users = () => {
const { dispatch, users } = useContext(ApiContext);
const contextValue = useContext(ApiContext);
useEffect(() => {
getUsers(true, dispatch);
}, [dispatch]);
console.log(contextValue, "Value from store");
return <div>Users</div>;
};
export default Users;
如何在上下文重新渲染时进行最佳优化?提前致谢!