How to convert the type Future<List<T>> to <List<T>> in fultter? - flutter

Question

everyone! I was developing e-commerce flutter app with doofinder APIs.
But I faced a thorny problem. I tried to get data from doofinder(it's just search service) API then present to screen. I added screen-shots.
Future<List<Product>> fetchProduct(query) async {
var response = await http.get(
Uri.parse(
'https://eu1-search.doofinder.com/5/search?hashid=30a5f&query=$query'),
// Send authorization headers to the backend.
headers: {'Authorization': 'c59dadc5d822ca2b134f170'},
);
if (response.statusCode == 200) {
// If the server did return a 200 OK response,
// then parse the JSON.
print(jsonDecode(response.body)['results'].toList().runtimeType);
return jsonDecode(response.body)['results'].toList().cast<List<Product>>();
} else {
// If the server did not return a 200 OK response,
// then throw an exception.
throw Exception('Failed to load album');
}
}
then,
onChanged: (_) => EasyDebounce.debounce(
'tFMemberController',
const Duration(milliseconds: 800),
() {
isSearchStarted =
textController!.text.isNotEmpty &&
textController!.text.trim().length > 0;
print('isSearchStarted $isSearchStarted');
if (isSearchStarted) {
print('${textController!.text.trim()}');
searchedProducts =
fetchProduct(textController!.text)
as List<Product>;
print(searchedProducts);
}
setState(() {});
},
),
And this is error log.
E/flutter ( 5295): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: type 'Future<List<Product>>' is not a subtype of type 'List<Product>' in type cast
E/flutter ( 5295): #0 _SearchPageState.build.<anonymous closure>.<anonymous closure> (package:s4s_mobileapp/search/page_search.dart:151:41)
E/flutter ( 5295): #1 EasyDebounce.debounce.<anonymous closure> (package:easy_debounce/easy_debounce.dart:44:22)
E/flutter ( 5295): #2 Timer._createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:18:15)
E/flutter ( 5295): #3 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:398:19)
E/flutter ( 5295): #4 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429:5)
E/flutter ( 5295): #5 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)
E/flutter ( 5295):
I/flutter ( 5295): List<dynamic>
E/flutter ( 5295): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: type 'CastList<dynamic, List<Product>>' is not a subtype of type 'FutureOr<List<Product>>'
E/flutter ( 5295): #0 fetchProduct (package:s4s_mobileapp/search/page_search.dart:41:58)
E/flutter ( 5295): <asynchronous suspension>
E/flutter ( 5295):
This makes me crazy.
I want you to take a closer look at the pictures below and find a suitable solution please.

Answer 1

Change
jsonDecode(response.body)['results'].toList().cast<List<Product>>();
to this:
jsonDecode(response.body)['results'].toList().cast<Product>();
The cast method already knows that you are working with lists and only wants to know the type of the elements, but not the type of the list itself.
EDIT: You also need to change:
searchedProducts = fetchProduct(textController!.text) as List<Product>;
to this:
searchedProducts = fetchProduct(textController!.text) as Future<List<Product>>;
You have to work with futures as your result is processed asynchronously. In the widget tree you have to use FutureBuilder which takes a future and builds your list as you want.