A⇒B⇒Zへ値を渡す
<index.js>
import React from 'react';
import ReactDOM from 'react-dom/client';
import Parent from './Parent';
import reportWebVitals from './reportWebVitals';
import { unstable_batchedUpdates } from 'react-dom' // or 'react-native'
const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
<React.StrictMode>
<Parent />
</React.StrictMode>
);
// If you want to start measuring performance in your Parent, pass a function
// to log results (for example: reportWebVitals(console.log))
// or send to an analytics endpoint. Learn more: https://bit.ly/CRA-vitals
reportWebVitals();
<Parent.js>
import {useState} from 'react';
import ChildComponentA from './ChildComponentA';
import ChildComponentB from './ChildComponentB';
import ChildComponentZ from './ChildComponentZ';
const Parent = ()=>{
const [val,setVal] = useState('');
const [valval,setValval] = useState(val);
return(
<div>
<ChildComponentA emitVal={setVal}/>
<ChildComponentB val = {val}
emitValval={setValval}/>
<ChildComponentZ valval = {valval}/>
</div>
);
}
export default Parent;
<ChildComponentA.js>
const ChildComponentA = (props)=>{
return(
<div>
<button type="button"
onClick={()=>props.emitVal(Math.random())}>
ランダムに値を親コンポーネントに送信
</button>
</div>
);
}
export default ChildComponentA;
<ChildComponentB.js>
const ChildComponentB = (props)=>{
return(
<div>
<p>受け取った値：{props.val}</p>
<button type="button"
onClick={()=>props.emitValval(props.val)}>
値を受け渡す
</button>
</div>
);
}
export default ChildComponentB;
<ChildComponentZ.js>
const ChildComponentZ = (props)=>{
return(
<div>
<p>受け取った値：{props.valval}</p>
</div>
);
}
export default ChildComponentZ;
