class MyComponent extends Component {

    constructor() {
        this.prop1 = this.props.prop1;
        this.prop2 = this.props.prop2;
    }

    render() {
        //....
    }

    onEvent(e) {
        this.setState({
            prop1: getProp1(),
            prop2: this.prop2()
        });
    }
}

class MyState {

    update(params) {
        this.prop1 = getProp1();
    }

}


class MyComponent extends Component {

    constructor() {
        this.state.obj = this.props.obj; // this has type MyState
    }

    render() {
        //....
    }

    onEvent(e) {
        this.obj.update(e.something);
        this.setState(this.obj);
    }
}