dart/flutter:: type 'Null' is not a subtype of type 'String' in type cast ERRor, not able to fetch data - flutter

Question

I am running into a "type 'Null' is not a subtype of type 'String' in type cast" when I try to retrieve the data.
not sure what the issue is... I think the data is not being found or something along those lines
source code:: https://github.com/casas1010/flutter_firebase_vendor_management
error message::
════════ Exception caught by widgets library ═══════════════════════════════════
The following _CastError was thrown building JobApplicationsListView(dirty):
type 'Null' is not a subtype of type 'String' in type cast
The relevant error-causing widget was
JobApplicationsListView
lib/…/job_applications/job_application_view.dart:75
When the exception was thrown, this was the stack
#0 new CloudJobApplication.fromSnapshot
package:ijob_clone_app/…/cloud/cloud_job_application.dart:27
#1 FirebaseCloudStorage.allJobApplications.<anonymous closure>.<anonymous closure>
package:ijob_clone_app/…/cloud/firebase_cloud_storage.dart:49
#2 MappedListIterable.elementAt (dart:_internal/iterable.dart:413:31)
#3 ListIterator.moveNext (dart:_internal/iterable.dart:342:26)
#4 WhereIterator.moveNext (dart:_internal/iterable.dart:438:22)
#5 Iterable.length (dart:core/iterable.dart:497:15)
#6 JobApplicationsListView.build
package:ijob_clone_app/…/widgets/job_application_list_widget.dart:27
#7 StatelessElement.build
package:flutter/…/widgets/framework.dart:4949
#8 ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4878
#9 Element.rebuild
package:flutter/…/widgets/framework.dart:4604
#10 ComponentElement._firstBuild
package:flutter/…/widgets/framework.dart:4859
#11 ComponentElement.mount
package:flutter/…/widgets/framework.dart:4853
#12 Element.inflateWidget
package:flutter/…/widgets/framework.dart:3863
#13 Element.updateChild
package:flutter/…/widgets/framework.dart:3586
#14 ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4904
#15 StatefulElement.performRebuild
package:flutter/…/widgets/framework.dart:5050
#16 Element.rebuild
package:flutter/…/widgets/framework.dart:4604
#17 BuildOwner.buildScope
package:flutter/…/widgets/framework.dart:2667
#18 WidgetsBinding.drawFrame
package:flutter/…/widgets/binding.dart:882
#19 RendererBinding._handlePersistentFrameCallback
package:flutter/…/rendering/binding.dart:378
#20 SchedulerBinding._invokeFrameCallback
package:flutter/…/scheduler/binding.dart:1175
#21 SchedulerBinding.handleDrawFrame
package:flutter/…/scheduler/binding.dart:1104
#22 SchedulerBinding._handleDrawFrame
package:flutter/…/scheduler/binding.dart:1015
#23 _invoke (dart:ui/hooks.dart:148:13)
#24 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:318:5)
#25 _drawFrame (dart:ui/hooks.dart:115:31)
════════════════════════════════════════════════════════════════════════════════
D/TrafficStats( 9769): tagSocket(99) with statsTag=0xffffffff, statsUid=-1
CloudJobApplication::
#immutable
class CloudJobApplication {
final String documentId;
final String jobApplicatorId;
final String jobApplicationState;
final String jobApplicationSubState;
const CloudJobApplication({
required this.documentId,
required this.jobApplicatorId,
required this.jobApplicationState,
required this.jobApplicationSubState,
});
// acts as constructor
CloudJobApplication.fromSnapshot(
QueryDocumentSnapshot<Map<String, dynamic>> snapshot)
: documentId = snapshot.id,
jobApplicatorId = snapshot.data()[jobApplicatorIdColumn] as String,
jobApplicationState =
snapshot.data()[jobApplicationStateColumn] as String,
jobApplicationSubState =
snapshot.data()[jobApplicationSubStateColumn] as String;
}
FirebaseCloudStorage::
class FirebaseCloudStorage {
final job = FirebaseFirestore.instance.collection('jobs');
final jobApplication =
FirebaseFirestore.instance.collection('job applications');
// This works perfect for getting the jobs
Stream<Iterable<CloudJob>> allJobs({required String jobCreatorId}) =>
job.snapshots().map((event) => event.docs
.map((doc) => CloudJob.fromSnapshot(doc))
.where((job) => job.jobCreatorId == jobCreatorId));
// this does not work. i copied the code from above and changed it
Stream<Iterable<CloudJobApplication>> allJobApplications() =>
jobApplication.snapshots().map((event) => event.docs
.map((doc) => CloudJobApplication.fromSnapshot(doc))
.where((jobApplication) =>
jobApplication.documentId == 'f2FvzZmr51v1wyrYZYoM'));
// singleton
static final FirebaseCloudStorage _shared =
FirebaseCloudStorage._sharedInstance();
FirebaseCloudStorage._sharedInstance();
factory FirebaseCloudStorage() => _shared;
}
JobApplicationsView:: ( this is where the issue starts, the issue appears when this widget tries to retrieve the data from the server i thin )
import 'package:flutter/material.dart';
import '../../services/cloud/cloud_job_application.dart';
import '../../utilities/widgets/job_application_list_widget.dart';
import '../../utilities/widgets/jobs_list_widget.dart';
import '/constants/routes.dart';
import '/enums/menu_action.dart';
import '/services/auth/auth_service.dart';
import '/services/cloud/cloud_job.dart';
import '/services/cloud/firebase_cloud_storage.dart';
import '/utilities/dialogs/logout_dialog.dart';
class JobApplicationsView extends StatefulWidget {
const JobApplicationsView({Key? key}) : super(key: key);
#override
_JobApplicationsViewState createState() => _JobApplicationsViewState();
}
class _JobApplicationsViewState extends State<JobApplicationsView> {
late final FirebaseCloudStorage _jobsService;
String get userId => AuthService.firebase().currentUser!.id;
#override
void initState() {
_jobsService = FirebaseCloudStorage();
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Your job applications'),
actions: [
IconButton(
onPressed: () {
// Navigator.of(context).pushNamed(createOrUpdateJobRoute);
},
icon: const Icon(Icons.add),
),
PopupMenuButton<MenuAction>(
onSelected: (value) async {
prin('code removed')
},
itemBuilder: (context) {
return const [
PopupMenuItem<MenuAction>(
value: MenuAction.logout,
child: Text('Log out'),
),
];
},
)
],
),
body: StreamBuilder(
stream: _jobsService.allJobApplications(),
builder: (context, snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.waiting:
case ConnectionState.active:
if (snapshot.hasData) {
final allJobs = snapshot.data as Iterable<CloudJobApplication>;
print(snapshot);
return JobApplicationsListView( // ERROR IS OCURRING HERE
jobs: allJobs,
);
return Text('results');
} else {
return const CircularProgressIndicator();
}
default:
return const CircularProgressIndicator();
}
},
),
);
}
}

Answer 1

Try like this
CloudJobApplication.fromSnapshot(
QueryDocumentSnapshot<Map<String, dynamic>> snapshot)
: documentId = snapshot.id,
jobApplicatorId = snapshot.data()[jobApplicatorIdColumn] ?? "",
jobApplicationState = snapshot.get(jobApplicationStateColumn) ?? "",
jobApplicationSubState =
snapshot.get(jobApplicationSubStateColumn) ?? "";