How to use Future<bool> in Widget - flutter

Question

I have a Future function in my Provider Repository. However it is Future<bool> since I need async for http request.
Future<bool> hasCard() async {
String token = await getToken();
var body = jsonEncode({"token": token, "userID": user.getUserID()});
var res = await http.post((baseUrl + "/hasCard"), body: body, headers: {
"Accept": "application/json",
"content-type": "application/json"
});
print(res.toString());
if (res.statusCode == 200) {
this.paymentModel = PaymentModel.fromJson(json.decode(res.body));
return true;
}
return false;
}
And in my Widget I want to check this value:
Widget build(BuildContext context) {
var user = Provider.of<UserRepository>(context);
if(user.hasCard())
{
//do something
}
But I get an error message:
Conditions must have a static type of 'bool'.dart(non_bool_condition)
Since it is a Widget type I cannot use async here. What could be the way to solve this?

Answer 1

You can use a FutureBuilder, it will build the widget according to the future value, which will be null until the future is completed. Here is an example.
FutureBuilder(
future: hasCard(),
builder: (context, snapshot) {
if (snapshot.data == null)
return Container(
width: 20,
height: 20,
child: CircularProgressIndicator());
if (snapshot.data)
return Icon(
Icons.check,
color: Colors.green,
);
else
return Icon(
Icons.cancel,
color: Colors.red,
);
},
)

Answer 2

Well not only for a Future<bool> for any other future you can use the FutureBuilder where the future is what returns you the type of future and snapshot is the data recieved from it.
FutureBuilder(
future: hasCard(),
builder: (context, snapshot) {
if (snapshot.data != null){
print(snapshot.data)}
else{
print("returned data is null!")}
},
)
and I would suggest assigning a default value to your bool.
good luck!