如何在 _app.js 中使用 getStaticProps 在 Next.js 的每个页面中显示从 api 获取的数据

Question

To be specific I am showing data on the navbar from the API endpoint. And I want to use getStaticProps to get those data on all the pages. But the problem is I need to do getStaticProps on all the pages.

Can we do something like this and get data on all the pages as props?

//pages/_app.js
function MyApp({ Component, pageProps, navs }) {
  return (
    <>
      <Component {...pageProps} navs={navs} />
    </>
  );
}
export async function getStaticProps() {
  const res = await api.get("/api/v1/navs");
  const navs = res.data;
  return {
    props: {
      navs,
    },
    // revalidate: 60, // In seconds
  };
}

export default MyApp;

What could be the alternative way of doing this? Is there a way to manage a global state, so that it is used by all the pages? I don't think we can use Context API to provide data to all the pages too.

Answer 1

Problem

NextJS doesn't currently support lifecycle methods in _app.js .

Solution

Since the above isn't supported yet, you'll want to create a reusable getStaticProps function and export it from all pages . Unfortunately, this does mean some WET code; however, you can reduce some boilerplate by creating a HOC which wraps the page and also exports a getStaticProps function.

Alternatives

You can use getInitialProps within the _app.js file. Unfortunately, this disables automatic static optimization across the entire application .

Demo

Code

components/Navigation

import * as React from "react";
import Link from "next/link";
import { nav, navItem } from "./Navigation.module.css";

const Navigation = () => (
  <div className={nav}>
    {[
      { title: "Home", url: "/" },
      { title: "About", url: "/about" },
      { title: "Help", url: "/help" }
    ].map(({ title, url }) => (
      <div className={navItem} key={title}>
        <Link href={url}>
          {/* eslint-disable-next-line jsx-a11y/anchor-is-valid */}
          <a>{title}</a>
        </Link>
      </div>
    ))}
  </div>
);

export default Navigation;

components/UsersList

import * as React from "react";
import isEmpty from "lodash.isempty";
import { noUsers, title, userList, user } from "./UsersList.module.css";

const UsersList = ({ error, users, retrieved }) =>
  !retrieved ? (
    <p>Loading...</p>
  ) : !isEmpty(users) ? (
    <div className={userList}>
      <h1 className={title}>Statically Optimized User List</h1>
      {users.map(({ name }) => (
        <div className={user} key={name}>
          {name}
        </div>
      ))}
    </div>
  ) : (
    <div className={noUsers}>{error || "Failed to load users list"}</div>
  );

export default UsersList;

containers/withUsersList

import * as React from "react";
import axios from "axios";
import UsersList from "../../components/UsersList";

/**
 * A HOC that wraps a page and adds the UserList component to it.
 *
 * @function withUsersList
 * @param Component - a React component (page)
 * @returns {ReactElement}
 * @example withUsersList(Component)
 */
const withUsersList = (Component) => {
  const wrappedComponent = (props) => (
    <>
      <UsersList {...props} />
      <Component {...props} />
    </>
  );

  return wrappedComponent;
};

export const getStaticProps = async () => {
  try {
    const res = await axios.get("https://jsonplaceholder.typicode.com/users");

    return {
      props: {
        retrieved: true,
        users: res.data,
        error: ""
      }
    };
  } catch (error) {
    return {
      props: {
        retrieved: true,
        users: [],
        error: error.toString()
      }
    };
  }
};

export default withUsersList;

pages/_app.js

import * as React from "react";
import Navigation from "../components/Navigation";

const App = ({ Component, pageProps }) => (
  <>
    <Navigation />
    <Component {...pageProps} />
  </>
);

export default App;

pages/about

import withUsersList, { getStaticProps } from "../containers/withUsersList";

const AboutPage = () => <div>About Us.</div>;

export { getStaticProps };

export default withUsersList(AboutPage);

pages/help

import withUsersList, { getStaticProps } from "../containers/withUsersList";

const HelpPage = () => <div>Find Help Here.</div>;

export { getStaticProps };

export default withUsersList(HelpPage);

pages/index

import withUsersList, { getStaticProps } from "../containers/withUsersList";

const IndexPage = () => <div>Hello World.</div>;

export { getStaticProps };

export default withUsersList(IndexPage);