在React中，this refers to the instance of the component that the component is a child of. In order to update the component, you need to call methods on the parent component that have access to the component's this reference.

Here's an example of how you can use this to update a child component:

```jsx import React from 'react';

class ChildComponent extends React.Component { render() { return (

class ParentComponent extends React.Component { constructor(props) { super(props); this.state = { count: 0 }; }

incrementCount() { this.setState({ count: this.state.count + 1 }); }

render() { return (

export default ParentComponent; ```

In this example, the ParentComponent has a state variable called count that is initially set to 0. The incrementCount method increments the count state variable by 1. The ChildComponent has a reference to the ParentComponent using thisrefs['ParentComponent'].

When the user clicks the "Increment count" button, the incrementCount method is called, which updates the count state variable and triggers the re-render of the ChildComponent. This will cause the child component to update with the new value of count.