onFieldSubmitted of TextFormFeild repetitive call upon calling future function - Flutter - flutter

Question

Scenario:
I have a TextFormFeild in which user write product name to search. If the searched product is not available in the database then I want to store that searched product in the database. To do that I have the function storeUserSearchedValue() which is calling future function inside it.
After looking googling this problem I have found that calling future during flutter's build phase causes repetitive invocations.
How can I store the value of the searched product in the database on the onFieldSubmitted function without facing non-stop repetirive invocation of the function?
Code
Class Displaying textfeild and and it's onFieldSubmitted function.
class SearchProductView extends StatefulWidget {
#override
_SearchProductViewState createState() => _SearchProductViewState();
}
class _SearchProductViewState extends State<SearchProductView> {
storeUserSearchedValue(String _userSearchedProduct,List<Product> _productsData) {
print("I N S I D E storeUserSearchedValue: " + _userSearchedProduct.toString());
int _noOfResultsOfUserProducts = 0;
for (int i = 0; i < _productsData.length; i++) {
if (_productsData[i].name.contains(_userSearchedProduct))
_noOfResultsOfUserProducts++;
}
if (_noOfResultsOfUserProducts == 0)
SearchviewModel().addCustomerSearchedProducts(_userSearchedProduct);
}
#override
Widget build(BuildContext context) {
final _allProductsData = Provider.of<List<Product>>(context);
return Scaffold(
............
TextFormField(
controller: _searchedProductText,
onFieldSubmitted:
storeUserSearchedValue(
_searchedProductText.text,
_allProductsData,
),
onChanged: searchOperation,
),
)
.........
}
Actual logic of storing data in the database
class SearchviewModel extends BaseViewModel {
// -------- Below Function are adding searched product in `customer` collection
addCustomerSearchedProducts(String searchedProductText) async {
String _currentUser = FirebaseAuth.instance.currentUser;
Map<String, dynamic> custdataMap = {
"custSearchedProducts": [searchedProductText, DateTime.now()]
};
await updateCustData(custdataMap, _currentUser.uid);
}
Future<bool> updateCustData(Map<String, dynamic> dataMap, String custID) async {
// - Dynamically adding data in the db
dataMap.forEach(
(key, value) async {
await FirebaseFirestore.instance.collection('customer').doc(custID).set(
{
key: value,
},SetOptions(merge: true),
);
},
);
return true;
}
}
Video representaion of problem

Answer 1

Simply adding this (_)=> (not this ()=>) with onFieldSubmitted property of textformfeild while calling storeUserSearchedValue function stop repetative invocations.
onFieldSubmitted: (_)=> storeUserSearchedValue(_searchedProductText.text,_allProductsData),
The above code snippet worked fine!
I'm not quite sure what is the reason behind it though