When you have to use class components, use the bind method to bind event handlers to the component instance. When defining event handlers in React, it is important to bind them to the component instance to ensure that the 'this' keyword refers to the correct object. This is because the default behavior of JavaScript is to bind 'this' to the object that triggered the event, which can cause issues when trying to access component state or props. By using the bind method, we can explicitly set the value of 'this' to the component instance, ensuring that we have access to the correct context.

Here is an example of how to use the bind method to bind an event handler to the component instance:

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

  handleClick() {
    this.setState(prevState => ({
      count: prevState.count + 1
    }));
  }

  render() {
    return (
      <button onClick={this.handleClick}>
        Click me
      </button>
    );
  }
}

In the above example, we define a handleClick method that updates the component state when the button is clicked. We then use the bind method in the constructor to bind the handleClick method to the component instance. This ensures that the 'this' keyword in the handleClick method refers to the component instance, allowing us to access the component state using 'this.state'.