Conditionally assign ref in react

Question

I'm working on something in react and have encountered a challenge I'm not being able to solve myself. I've searched here and others places and I found topics with similar titles but didn't have anything to do with the problem I'm having, so here we go:

So I have an array which will be mapped into React, components, normally like so:

export default ParentComponent = () => {

//bunch of stuff here and there is an array called arr

return (<>
 
    {arr.map((item, id) => {<ChildComponent props={item} key={id}>})}

</>)

}

but the thing is, there's a state in the parent element which stores the id of one of the ChildComponents that is currently selected (I'm doing this by setting up a context and setting this state inside the ChildComponent), and then the problem is that I have to reference a node inside of the ChildComponent which is currently selected. I can forward a ref no problem, but I also want to assign the ref only on the currently selected ChildComponent, I would like to do this:

export default ParentComponent = () => {

//bunch of stuff here and there is an array called arr and there's a state which holds the id of a  selected ChildComponent called selectedObjectId

const selectedRef = createRef();

return (<>
    <someContextProvider>
    {arr.map((item, id) => {
       <ChildComponent 
        props={item} 
        key={id} 
        ref={selectedObjectId == id ? selectedRef : null}
       >
    })}
   <someContextProvider />
</>)

}

But I have tried and we can't do that. So how can dynamically assign the ref to only one particular element of an array if a certain condition is true?

Answer 1

You can use the props spread operator {...props} to pass a conditional ref by building the props object first. E.g.

export default ParentComponent = () => {
  const selectedRef = useRef(null);

  return (
    <SomeContextProvider>
      {arr.map((item, id) => {
        const itemProps = selectedObjectId == id ? { ref: selectedRef } : {};
        return ( 
          <ChildComponent 
            props={item} 
            key={id} 
            {...itemProps}
          />
        );
      })}
    <SomeContextProvider />
  )
}