Kuunganisha Viingilio kwa Safu katika React

Acha katika hali notes ihifadhi safu:

jsxfunction App() {
  const [notes, setNotes] = useState([1, 2, 3]);
  
  return <div>
    
  </div>;
}

Acha tuwe pia na kitendo saidizi, kinachopata jumla ya vipengele vya safu:

jsxfunction getSum(arr) {
  let sum = 0;
  
  for (const elem of arr) {
    sum += +elem;
  }
  
  return sum;
}

function App() {
  ...
}

Wacha tupate na tuonyeshe jumla ya vipengele vya safu yetu kutoka kwenye hali, tukitumia kitendo chetu saidizi:

jsxfunction App() {
  const [notes, setNotes] = useState([1, 2, 3]);
  
  return <div>
    {getSum(notes)}
  </div>;
}

Wacha sasa tutengeneze viingilio vitatu na kwenye value kila kikiingiza andika kipengele kimoja cha safu:

jsxfunction App() {
  const [notes, setNotes] = useState([1, 2, 3]);
  
  return <div>
    <input value={notes[0]} />
    <input value={notes[1]} />
    <input value={notes[2]} />
    
    {getSum(notes)}
  </div>;
}

Wacha sasa tuongeze tukio onChange kwenye viingilio vyetu. Wakati huu tutafanya kitendo kimoja cha pamoja kinachoshughulikia tukio hili:

jsxfunction App() {
  const [notes, setNotes] = useState([1, 2, 3]);
  
  function changeHandler(index, event) {
    // kitendo cha pamoja kinachoshughulikia
  }
  
  return <div>
    <input value={notes[0]} onChange={event => changeHandler(0, event)} />
    <input value={notes[1]} onChange={event => changeHandler(1, event)} />
    <input value={notes[2]} onChange={event => changeHandler(2, event)} />
    
    {getSum(notes)}
  </div>;
}

Kama unavyoona, kitendo changeHandler hupokea nambari ya kwanza ya kipengele cha safu, ambacho kikiingiza kinaharakisha.

Kwa nambari hii tunaweza kubadilisha kipengele cha safu kwa yaliyomo kwenye kikiingiza.

Wacha tutengeneze hii:

jsxfunction changeHandler(index, event) {
  setNotes([...notes.slice(0, index), event.target.value, ...notes.slice(index + 1)]);
}

Sasa itawezekana kuhariri kikiingiza chochote, wakati huu safu itabadilika kwa nguvu na, ipasavyo, jumla ya vipengele vyake itakokotolewa upya.

Wacha tukusanye msimbo wetu wote pamoja:

jsxfunction App() {
  const [notes, setNotes] = useState([1, 2, 3]);
  
  function changeHandler(index, event) {
    setNotes([...notes.slice(0, index), event.target.value, ...notes.slice(index + 1)]);
  }
  
  return <div>
    <input value={notes[0]} onChange={event => changeHandler(0, event)} />
    <input value={notes[1]} onChange={event => changeHandler(1, event)} />
    <input value={notes[2]} onChange={event => changeHandler(2, event)} />
    
    {getSum(notes)}
  </div>;
}

Inawezekana kufanya hivi, ili viingilio vitengenezwe kwenye kitanzi:

jsxfunction App() {
  const [notes, setNotes] = useState([1, 2, 3]);
  
  function changeHandler(index, event) {
    setNotes([...notes.slice(0, index), event.target.value, ...notes.slice(index + 1)]);
  }
  
  const result = notes.map((note, index) => {
    return <input
      key={index}
      value={note}
      onChange={event => changeHandler(index, event)}
    />;
  });
  
  return <div>
    {result}
    {getSum(notes)}
  </div>;
}

jsx[1, 2, 3, 4, 5, 6, 7, 8, 9]