Flutter&Dart Catch Block does not catch thrown Exception - flutter

Question

I am trying to catch thrown exception when server does not return 200 status code. Here is the code:
late Future<List<Data>> datasFuture;
String _warning = "";
#override
void initState() {
try {
datasFuture = RestfulServiceProvider.fetchDatas();
} on Exception {
_warning = "There is no data to fetch!";
}
super.initState();
}
//RestfulServiceProvider class
static Future<List<Data>> fetchDatas() async {
List jsonResponse = [];
final response =
await http.get(Uri.parse('http://localhost:8080/datas'));
if (response.statusCode == 200) {
jsonResponse = json.decode(response.body);
return jsonResponse.map((data) => Data.fromJson(data)).toList();
} else {
throw Exception();
}
}
When exception occurs code does not go in on Exception block, I cant handle the error. Any idea or solutions? thanks.

Answer 1

Try-catch block can catch exceptions occured in the bounds of its block. Your will not catch error because you are just assigning Future to a variable ( not awaiting its value ). So can the block catch exceptions from single assignment operation? No. Variable is just assigned and the program moves on and quits try-catch block immediately. You must await the value to catch it the block - awaiting it. But you can not use async-await syntax directly inside initState. So you have 2 options:
catchError of Future
RestfulServiceProvider.fetchDatas().catchError((error){Your code here}));
Utilizing it into another function with async-await
void someFunc () async{
try {
await RestfulServiceProvider.fetchDatas();
} on Exception catch(e) {
_warning = "There is no data to fetch!";
}
}
And call it in initState