Hi i am adding Material UI to Next.js. I followed the example from the Next Js git hub along with a youtube tutorial. The error im getting is ....
Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.
And here is the code from the _document.js
import React from 'react';
import Document, { Html, Head, Main, NextScript } from 'next/document';
import { ServerStyleSheets } from '@material-ui/core/styles';
import theme from '../src/theme';
export default class MyDocument extends Document {
render() {
return (
<Html lang="en">
<Head>
{/* PWA primary color */}
<meta name="theme-color" content={theme.palette.primary.main} />
<link
rel="stylesheet"
href="https://fonts.googleapis.com/css?family=Roboto:300,400,500,700&display=swap"
/>
</Head>
<body>
<Main />
<NextScript />
</body>
</Html>
);
}
}
// `getInitialProps` belongs to `_document` (instead of `_app`),
// it's compatible with server-side generation (SSG).
MyDocument.getInitialProps = async (ctx) => {
// Resolution order
//
// On the server:
// 1. app.getInitialProps
// 2. page.getInitialProps
// 3. document.getInitialProps
// 4. app.render
// 5. page.render
// 6. document.render
//
// On the server with error:
// 1. document.getInitialProps
// 2. app.render
// 3. page.render
// 4. document.render
//
// On the client
// 1. app.getInitialProps
// 2. page.getInitialProps
// 3. app.render
// 4. page.render
// Render app and page and get the context of the page with collected side effects.
const sheets = new ServerStyleSheets();
const originalRenderPage = ctx.renderPage;
ctx.renderPage = () =>
originalRenderPage({
enhanceApp: (App) => (props) => sheets.collect(<App {...props} />),
});
const initialProps = await Document.getInitialProps(ctx);
return {
...initialProps,
// Styles fragment is rendered after the app and page rendering finish.
styles: [...React.Children.toArray(initialProps.styles), sheets.getStyleElement()],
};
};
Code from error page -
pages/_document.js (57:4) @ Object.ctx.renderPage
55 |
56 | ctx.renderPage = () =>
> 57 | originalRenderPage({
| ^
58 | enhanceApp: (App) => (props) => sheets.collect(<App {...props} />),
59 | });
60 |
It has now been resolved. Although the error was showing on the app.js page it was fixed by removing brackets from {link} import on my index page.
