What could be causing the error message about undefined classes to appear?

Just started using React and I'm encountering an error with undefined classes. Can someone help me understand why this is happening?

Here's the code snippet for reference:

const styles = (theme) => ({
    root: {
      width: "100%",
      marginTop: theme.spacing.unit * 3,
      overflowX: "auto"
    },
    table: {
      minWidth: 700
    },
    tableRow: {
      "&.Mui-selected, &.Mui-selected:hover": {
        backgroundColor: "purple",
        "& > .MuiTableCell-root": {
          color: "yellow"
        }
      }
    }
  });
export default function MyTable(props) {
    const { classes } = props;
    return (
        <div>
            <Box>
                <TableContainer component={Paper}>
                    <Table className={classes.table}>

I keep running into uncaught runtime errors because classes.table is undefined. Any tips on what might be causing this issue?

reactjsmaterial-ui

Answer №1

The lack of a classes property being passed to the MyTable component, as pointed out in the comments, is causing the issue where classes cannot be destructured from props and returns undefined.

To resolve this, utilize the makeStyles and createStyles functions available in @material-ui/core/styles.

import { makeStyles, createStyles } from "@material-ui/core/styles";

const useStyles = makeStyles((theme: Theme) =>
  createStyles({
    root: {
      width: "100%",
      marginTop: theme.spacing.unit * 3,
      overflowX: "auto",
    },
    table: {
      minWidth: 700,
    },
    tableRow: {
      "&.Mui-selected, &.Mui-selected:hover": {
        backgroundColor: "purple",
        "& > .MuiTableCell-root": {
          color: "yellow",
        },
      },
    },
  })
);

With the useStyles hook, you can now access the classes within your component.

export default function MyTable(props) {
  const classes = useStyles();
  return (
    <div>
      <Box>
        <TableContainer component={Paper}>
          <Table className={classes.table}>
            ...
          </Table>
        </TableContainer>
      </Box>
    </div>
  );
}

Visit MUI v4 styles basics for further insights.

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