How to deal with a ref within a loop?

Question

Below is my parent component with multiple inputs from a loop. How can I choose one input to focus? Do I have to create a dynamic ref in this case?

Answer 1

Using a general useFocus hook

// General Focus Hook
const useFocus = (initialFocus = false, id = "") => {
    const [focus, setFocus] = useState(initialFocus)
    return ([
        (newVal=true) => setFocus(newVal), {
            autoFocus: focus,
            key: `${id}${focus}`,
            onFocus: () => setFocus(true),
            onBlur: () => setFocus(false),
        },
    ])
}

const data: [{
        name: "abc"
    },{ 
        name: "def" 
}]

const TestRef = () => {

    const focusHelper = data.map( (_,i) => {
        const [setFocus, focusProps]= useFocus(false, i)
        return {setFocus, focusProps}
    }) 

    return (
      <div>
        {data.map( (o,i) => (
          <Hello placeholder={o.name} {...focusHelper[i].focusProps} />;
        ))}
        <button onClick={() => focusHelper[0].setFocus()}>focus input 1</button>
        <button onClick={() => focusHelper[1].setFocus()}>focus input 2</button>
      </div>
    );
}

You can find more info here: Set focus on input after render

Answer 2

You can use callback refs to generate and store the dynamic ref of each input in an array. Now you can refer to them using the index of the ref:

const Hello = React.forwardRef((props,  ref) => <input ref={ref} />);

class Button extends React.Component {
  onClick = () => this.props.onClick(this.props.id);

  render() {
    return (
      <button onClick={this.onClick}>{this.props.children}</button>
    );
  }
}

class TestRef extends React.Component {
  state = {
    data: [
      {
        name: "abc"
      },
      { name: "def" }
    ]
  };
  
  inputRefs = [];
  
  setRef = (ref) => {
    this.inputRefs.push(ref);
  };
  
  focusInput = (id) => this.inputRefs[id].focus();
  
  render() {
    return (
      <div>
        {this.state.data.map(({ name }) => (
          <Hello 
            placeholder={name} 
            ref={this.setRef} 
            key={name} />
        ))}
        <Button onClick={this.focusInput} id={0}>focus input 1</Button>
        <Button onClick={this.focusInput} id={1}>focus input 2</Button>
      </div>
    );
  }
}

ReactDOM.render(<TestRef />, document.getElementById("root"));

<script crossorigin src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>

<div id="root"></div>

Answer 3

I discovered another way of tackling this:

let dataCount = 0;

class TestRef extends React.Component {
  state = {
    data: [
      {
        name: "abc"
      },
      { name: "def" }
    ]
  };
  focusInput = (thisHello) => this[`ref${thisHello}`].current.focus();
  render() {
    return (
      <div>
        {this.state.data.map(o => {
          dataCount++
          return <Hello placeholder={o.name} ref={(el) => { this[`ref${dataCount}`] = el; }} />;
        })}
        <button onClick={() => this.focusInput(1)}>focus input 1</button>
        <button onClick={() => this.focusInput(2)}>focus input 2</button>
      </div>
    );
  }
}

The dataCount is unnecessary if your Hello element has a key or unique ID to use as a variable.

Answer 4

if you are coming to this question 2020 here is how you create multiple refs using create hooks in a loop

   const MyComponent=(){
    // empty list to put our refs in
    let LiRefs = []

    return (
        <React.Fragment>
          <ul className="event-list">
// this part i am checking if my data exist first other wise load spinner 
            {newData ? (
              newData.map((D) => {
// the cool part inside the loop 
//create new ref 
//push it into arr 

                const newRef = createRef();
                LiRefs.push(newRef);
                return (
// link it to ur li 
// voila you have list of refs that points to your list items 
                  <li key={D._id} ref={newRef}>
                    title : {D.title} <br />
                    description : {D.description}
                    <br />
                    data : {D.date} <br />
                    price : {D.price}
                    <br />
                    <div>creator : {D.creator.username}</div>
                    {authData.token && (
                      <button type="button" id={D._id} onClick={handelBooking}>
                        Book
                      </button>
                    )}
                  </li>
                );
              })
            ) : (
              <Spinner />
            )}
          </ul>
        </React.Fragment>
      );
 }