Future<List<dynamic>> cannot be assigned to List<dynamic> - flutter

Question

Getting the error (title) when I try to assign the return of this method to a widget parameter. The suggestions: is expect a List<dynamic> not a Future<List<dynamic>>. Is FutureBuilder the only way? The AutoCompleteTextField in this widget is a type ahead so will be calling getLocationSuggestionsList every .5 seconds after keystrokes stop (not sure if that matters in answering this question).
#override
Widget build(BuildContext context) {
return Container(
child: new Center(
child: Column(children: <Widget>[
new Column(children: <Widget>[
searchTextField = AutoCompleteTextField<dynamic>(
suggestions: getLocationSuggestionsList("sd"),
style: new TextStyle(color: Colors.black, fontSize: 16.0),
decoration: new InputDecoration(
.....
Future<List<dynamic>> getLocationSuggestionsList(String locationText) async {
List<String> suggestionList = List();
Map suggestionsKeyValuePairs = Map<String, String>();
dynamic data = await GoogleMapsServices.getAddressPrediction(
locationText,
LatLng(currentLocation.latitude, currentLocation.longitude),
);
if (data != null) {
for (dynamic predictions in data.predictions) {
suggestionsKeyValuePairs[predictions.description] = predictions.placeId;
if (!suggestionList.contains(predictions.description))
suggestionList.add(predictions.description);
}
return suggestionList;
} else {
return [''];
}
}

Answer 1

The cause for this error is that the suggestions parameter expects a List not a Future.
What you can do is create a state variable and assign the result of your getLocationSuggestionsList() function to that with a setState() call or any other state management mechanism so that whenever the state changes the UI builds again with the relevant data.
class YourClass extends StatefulWidget {
///
}
class _YourClassState extends State<YourClass>{
/// Your state variable here. Initialize with data that will be showing if actual data not available.
List<dynamic> suggestionList = ["];
initState(){
/// call you get suggestion function on init or any other lifecycle methods as per your need, may be inside build
getLocationSuggestionsList("sd");
super.initState();
}
#override
Widget build(context){
return AutoCompleteTextField<dynamic>(
suggestions: suggestionList,
style: new TextStyle(color: Colors.black, fontSize: 16.0),
decoration: new InputDecoration()
/// ....
);
}
void getLocationSuggestionsList(String locationText) async {
List<String> sList = List();
Map suggestionsKeyValuePairs = Map<String, String>();
dynamic data = await GoogleMapsServices.getAddressPrediction(
locationText,
LatLng(currentLocation.latitude, currentLocation.longitude),
);
if (data != null) {
for (dynamic predictions in data.predictions) {
suggestionsKeyValuePairs[predictions.description] = predictions.placeId;
if (!sList.contains(predictions.description))
sList.add(predictions.description);
}
} else {
sList = [''];
}
setState((){
suggestionList = List;
/// This will render your UI again with updates suggestionList
});
}
}

Answer 2

getLocationSuggestionsList() is async and return a future, if you want to get the result (List<dynamic>), you need to call it with await keyword.
await getLocationSuggestionsList("sd")
But, this is only possible into async functions/methods.
You can resolve this by many ways:
Use FutureBuilder
Do it with reactive programing architecture (Bloc, Rx, raw streams, etc...)
Do it like krishnakumarcn ;) https://stackoverflow.com/a/62187158/13569191