useImperativeHandle

useImperativeHandle.md

The useImperativeHandle hook can be useful in advanced scenarios where you need to provide a custom instance to the parent of a functional component that is wrapped in a forwardRef.

For example, suppose you have a TextInput component that is implemented as a functional component and wrapped in a forwardRef so that it can be used like this:

const TextInput = React.forwardRef((props, ref) => {
  // The TextInput component implementation goes here
});

// Use the TextInput component with a ref
const inputRef = useRef(null);
<TextInput ref={inputRef} />

In this example, the TextInput component is wrapped in a forwardRef so that it can be used with a ref like any other element or component. However, because TextInput is a functional component, the ref that is passed to it will not be a reference to the instance of the TextInput component. Instead, it will be a reference to the DOM element that the TextInput component renders.

If you want the parent component to be able to access the instance of the TextInput component, you can use the useImperativeHandle hook inside the TextInput component to provide a custom instance to the parent. Here is an example of how this could be done:

const TextInput = React.forwardRef((props, ref) => {
  // The TextInput component implementation goes here

  // Create a ref to the input element
  const inputRef = useRef(null);

  // Provide a custom instance to the parent
  useImperativeHandle(ref, () => ({
    focus: () => {
      inputRef.current.focus();
    },
  }));

  return (
    <input ref={inputRef} />
  );
});

// Use the TextInput component with a ref
const inputRef = useRef(null);
<TextInput ref={inputRef} />

In this example, the useImperativeHandle hook is used inside the TextInput component to provide a custom instance to the parent. The custom instance has a focus method that can be used to focus the input element that the TextInput component renders.

To use the custom instance, the parent component can call the useImperativeHandle hook with the ref that it passed to the TextInput component, and then call the focus method on the returned instance. For example:

useImperativeHandle(inputRef, () => inputRef.current.focus());

This advanced use of the useImperativeHandle hook allows the parent component to access the instance of the TextInput component and call its methods, even though the TextInput component is implemented as a functional component and wrapped in a forwardRef.