input value not updating when mutating state - reactjs

Question

While creating a little project for learning purposes I have come across an issue with the updating of the input value. This is the component (I have tried to reduce it to a minimum).
function TipSelector({selections, onTipChanged}: {selections: TipSelectorItem[], onTipChanged?:(tipPercent:number)=>void}) {
const [controls, setControls] = useState<any>([]);
const [tip, setTip] = useState<string>("0");
function customTipChanged(percent: string) {
setTip(percent);
}
//Build controls
function buildControls()
{
let controlList: any[] = [];
controlList.push(<input className={styles.input} value={tip.toString()} onChange={(event)=> {customTipChanged(event.target.value)}}></input>);
setControls(controlList);
}
useEffect(()=>{
console.log("TipSelector: useEffect");
buildControls();
return ()=> {
console.log("unmounts");
}
},[])
console.log("TipSelector: Render -> "+tip);
return (
<div className={styles.tipSelector}>
<span className={globalStyles.label}>Select Tip %</span>
<div className={styles.btnContainer}>
{
controls
}
</div>
</div>
);
}
If I move the creation of the input directly into the return() statement the value is updated properly.

Answer 1

I'd move your inputs out of that component, and let them manage their own state out of the TipSelector.
See:
https://codesandbox.io/s/naughty-http-d38w9
e.g.:
import { useState, useEffect } from "react";
import CustomInput from "./Input";
function TipSelector({ selections, onTipChanged }) {
const [controls, setControls] = useState([]);
//Build controls
function buildControls() {
let controlList = [];
controlList.push(<CustomInput />);
controlList.push(<CustomInput />);
setControls(controlList);
}
useEffect(() => {
buildControls();
return () => {
console.log("unmounts");
};
}, []);
return (
<div>
<span>Select Tip %</span>
<div>{controls}</div>
</div>
);
}
export default TipSelector;
import { useState, useEffect } from "react";
function CustomInput() {
const [tip, setTip] = useState("0");
function customTipChanged(percent) {
setTip(percent);
}
return (
<input
value={tip.toString()}
onChange={(event) => {
customTipChanged(event.target.value);
}}
></input>
);
}
export default CustomInput;

Answer 2

You are only calling buildControls once, where the <input ... gets its value only that single time.
Whenever React re-renders your component (because e.g. some state changes), your {controls} will tell React to render that original <input ... with the old value.
I'm not sure why you are storing your controls in a state variable? There's no need for that, and as you noticed, it complicates things a lot. You would basically require a renderControls() function too that you would replace {controls} with.