Dirty state error in flutter - dart

Question

fifth.dart
import 'package:flutter/material.dart';
import 'package:emas_app/Dependant.dart' as Dep;
import 'package:emas_app/crm_dependent_list_model.dart';
import 'dart:convert';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'package:emas_app/crm_dep_entitlement_model.dart';
final String url = "http://crm.emastpa.com.my/MemberInfo.json";
//Future to get list of dependent names
Future<List<DependantModel>> fetchUserInfo() async{
http.Response response = await http.get(url);
var responsejson = json.decode(response.body);
return(responsejson[0]['Dependents'] as List)
.map((user) => DependantModel.fromJson(user))
.toList();
}
class Fifth extends StatefulWidget {
#override
_FifthState createState() => _FifthState();
}
class _FifthState extends State<Fifth> {
static Future<List<DependantModel>> depState;
#override
void initState() {
depState = fetchUserInfo();
super.initState();
}
#override
Widget build(BuildContext context) {
//ListView.builder inside FutureBuilder
var futureBuilder = new FutureBuilder<List<DependantModel>>(
future: depState,
builder: (context, snapshot){
switch(snapshot.connectionState){
case ConnectionState.none:
case ConnectionState.waiting:
return new Center(
child: new CircularProgressIndicator(),
);
default:
if(snapshot.hasError){
return new Text(snapshot.error);
}else{
List<DependantModel> user = snapshot.data;
return new ListView.builder(
itemCount: user.length,
itemBuilder: (context, index){
return new Column(
children: <Widget>[
new ListTile(
title: new Text(user[index].name,
style: TextStyle(fontSize: 20.0)),
subtitle: new Text(user[index].relationship,
style: TextStyle(fontSize: 15.0)),
trailing: new MaterialButton(color: Colors.greenAccent,
textColor: Colors.white,
child: new Text("More"),
onPressed: (){
Navigator.push(context,
new MaterialPageRoute(builder: (context) => Dep.Dependents(name: user[index].name)));
}
),
)
],
);
});
}
}
});
return new Scaffold(
body: futureBuilder,
);
}
}
I've just had the following error occurring in my flutter project.
I/flutter (12737): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (12737): The following assertion was thrown building FutureBuilder>(dirty, state:
I/flutter (12737): _FutureBuilderState>#b09b6):
I/flutter (12737): type 'NoSuchMethodError' is not a subtype of type 'String'
I/flutter (12737): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter (12737): more information in this error message to help you determine and fix the underlying cause.
I/flutter (12737): In either case, please report this assertion by filing a bug on GitHub:
what is dirty state?

Answer 1

As the error suggests, NoSuchMethodError, you have assigned the results of Future to a variable but the FutureBuilder expects future asynchronous computation to which this builder is currently connected and depState is not a method. You can directly set future: fetchUserInfo in FutureBuilder
Try this,
#override
Widget build(BuildContext context) {
var futureBuilder = new FutureBuilder<List<DependantModel>>(
future: fetchUserInfo, //your Future method
builder: (context, snapshot){
//Your code goes here
}
});
return new Scaffold(
body: futureBuilder,
);
}