import { Theme , WithStyles , withStyles } from "@material-ui/core" ; import { StyleRules } from "@material-ui/core/styles" ; import * as React from "react" ; const styles = ( theme ) : StyleRules => ( { root : { fontSize : '35px' } } ) ; interface IMyState { state : string ; } interface IMyProps extends WithStyles < typeof styles > { prop : string ; } class MyComponent extends React . Component < IMyProps , IMyState > { public render ( ) { const { classes } = this . props ; return ( < div className = { classes . root } > Hello TS , env : { process . env . REACT_APP_MY_ENV } < /div>); } } export default withStyles ( styles ) ( MyComponent ) ;