Why, exactly, do we need React.forwardRef? - reactjs

Question

Let's say I have a component with a scrollable subcomponent, and I want to expose the ability to scroll:
const MyComponent = (props) => {
return <ScrollView ... />
}
I want to be able to do
<MyComponent ref={myRef} />
...
myRef.scrollTo({x: 0});
So I need a way to forward the ref to the <ScrollView>. Let's try putting the ref on the props:
const MyComponent = (props) => {
return <ScrollView ref={props.scrollRef} ... />
}
...
<MyComponent scrollRef={myRef} />
...
myRef.scrollTo({x: 0});
I just tried that with React Native on iOS, and it indeed works. I see several advantages over React.forwardRef:
Simpler, because I don't need to use another React API.
Works also if there is more than one child who needs ref forwarding.
Seems to me that this approach is
What's the advantage of React.forwardRef? Why was it added in React 16.3?

Answer 1

Note that there is no difference between using another named prop like innerRef FOR FORWARDING, it works the same.
Refactoring class components
Since React moved toward function components (hooks) you might want to refactor the class component code to a function component without breaking the API.
// Refactor class component API to function component using forwardRef
<Component ref={myRef} />
React.forwardRef will be your only option (further explained in details).
Clean API
As a library author you may want a predictable API for ref forwarding.
For example, if you implemented a Component and someone wants to attach a ref to it, he has two options depending on your API:
<Component innerRef={myRef} />
The developer needs to be aware there is a custom prop for forwarding
To which element the innerRef attached? We can't know, should be mentioned in the API or we console.log(myRef.current)
<Component ref={myRef} />
Default behavior similar to ref prop used on HTML elements, commonly attached to the inner wrapper component.
Notice that React.forwardRef can be used for function component and HOC (for class component see alternative below).
Ref forwarding is not limited to DOM components. You can forward refs to class component instances, too.
For function components, forwardRef sometimes comes with useImperativeHandle combo (in class component you just call the class methods on ref instance: ref.current.myAttr().
// Same usage
<Component ref={myRef} />
const Component = React.forwardRef((props, ref) => {
// you can forward ref <div ref={ref} />
// you can add custom attributes to ref instance with `useImperativeHandle`
// like having ref.myAttribute() in addition to ones attached to other component.
});
Important behavior of ref prop without forwardRef.
For the class component, this code alone will attach the ref to CLASS INSTANCE which is not useful by itself and need another ref for forwarding:
// usage, passing a ref instance myRef to class Component
<Component ref={myRef} />
Full example, check the logs:
// We want to forward ref to inner div
class ClassComponent extends React.Component {
innerRef = React.createRef();
render() {
// Notice that you can't just `this.props.ref.current = node`
// You don't have `ref` prop, it always `undefined`.
return <div ref={this.innerRef}>Hello</div>;
}
}
const Component = () => {
const ref = React.useRef();
useEffect(() => {
// The ref attached to class instance
console.log(ref.current);
// Access inner div through another ref
console.log(ref.current.innerRef);
}, []);
return <ClassComponent ref={ref} />;
};
In function components, it won't even work because functions don't have instances.
By default, you may not use the ref attribute on function components because they don’t have instances. [1]
forwardRef.
Refs and the DOM.
Why we need ref forwarding?