Trigger Child component method when prop changes - reactjs

Question

I'm trying to make a child functional component to update when a Parent component changes a value in its state that I'm passing to a this child component as a prop.
The child component "receives" the value correctly and displays the prop value, but the method does not run again.
Child component
import React from 'react'
const MyCustomTable = props => {
const {
data = [],
} = props
const finalData = getSalesData() //This is the method i want to run when the selectedMonth prop updates
const getSalesData = () => {
//It does some calculations with the prop called data
}
return (
<Box>
{JSON.stringify(props.selectedMonth.value)}
<Table
data={finalData}
/>
</Box>
)
}
SalesByFamilyBU.propTypes = {}
export default MyCustomTable
The JSON.stringify line displays the changes correctly but I guess the getSalesData() is not automatically executed.

Answer 1

While you could use some lifecycle method or the useEffect hook to achieve what you want to do, I would rather use a functional approach.
In your example, finalData is a derived value of props.data and props.selectedMonth. You could then compute finalData directly from these props:
const MyCustomTable = props => {
const {
data = [],
} = props;
const filterData = (data, selectedMonth) => data.map(dataPoint => ({
...dataPoint,
selected: dataPoint.month === selectedMonth,
}); // or whatever, use your function logic here
const finalData = filterData(data, props.selectedMonth.value);
return (...);
};
If you really needed to call a function each time data is changing (ex. to fetch data elsewhere) you could use something like that:
const MyComponent = ({ data }) => {
const [finalData, setFinalData] = useState([]);
const myFunction = () => {
const newData = ... // whatever you need to do
setFinalData(newData);
};
useEffect(myFunction, [data]);
return ...;
};