How to remove or update selected object in list? - dart

Question

I made a simple flutter app, I have a screen and a listView, and data in the list can be deleted or updated.
But when i try to update or remove one of them, all my data in list being updated/deleted, what did i missed?
I do the following:
ListTile(
title: Text(child.name.toString()),
subtitle: Text('${child.amount}'),
onTap: () => _onChildTap(child),
trailing: GestureDetector(
onTap: () { setState(() { children.remove(child); }); },
child: Icon(Icons.delete)
),
)
void _onChildTap(ChildModel child) {
double amount = 5;
setState(() { child.amount += amount; });
}
For update and delete the data.
Below is my full code:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(primarySwatch: Colors.blue),
home: MyScreen()
);
}
}
class ParentModel {
ParentModel({this.id, this.name, this.children});
int id;
String name;
List<ChildModel> children;
}
class ChildModel {
ChildModel({this.id, this.name, this.amount});
int id;
String name;
double amount;
}
class MyScreen extends StatefulWidget {
#override
_MyScreenState createState() => _MyScreenState();
}
class _MyScreenState extends State<MyScreen> {
List<ParentModel> _list = [];
void _onAdd() {
ChildModel child = ChildModel(id: 1, name: 'Child 1', amount: 1);
List<ChildModel> children = [];
children.add(child);
List<ParentModel> results = [];
results.add(ParentModel(id: 1, name: 'Parent 1', children: children));
results.add(ParentModel(id: 2, name: 'Parent 2', children: children));
results.add(ParentModel(id: 3, name: 'Parent 3', children: children));
if (_list.isEmpty) {
setState(() { _list.addAll(results); });
}
else{
results.forEach((parent) {
if (!_isExistInParentList(parent.id)) {
setState(() { _list.add(parent); });
}
else {
parent.children.forEach((child) {
if (!_isExistInChildList(parent.id, child.id)) {
setState(() {
_list.firstWhere((parent) => parent.id == parent.id).children.add(child);
});
}
});
}
});
}
}
bool _isExistInParentList(int parentId) {
for (ParentModel parent in _list) {
if (parent.id == parentId) { return true; }
}
return false;
}
bool _isExistInChildList(int parentId, int childId) {
for (ParentModel parent in _list) {
if (parent.id == parentId) {
for (ChildModel child in parent.children) {
if (child.id == childId) {
return true;
}
}
}
}
return false;
}
void _onChildTap(ChildModel child) {
double amount = 5;
setState(() { child.amount += amount; });
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Flutter List'),
actions: <Widget>[
IconButton(
icon: Icon(Icons.add),
onPressed: _onAdd
)
],
),
body: Column(
children: <Widget>[
Expanded(
child: ListView.builder(
itemCount: _list.length,
itemBuilder: (context, index) {
ParentModel parent = _list[index];
return Column(
children: <Widget>[
ExpansionTile(
title: Text(parent.name),
initiallyExpanded: true,
children: _buildChildren(parent.children)
),
SizedBox(height: 10)
],
);
}
),
),
],
),
);
}
List<Widget> _buildChildren(List<ChildModel> children) {
List<Widget> widgets = [];
children.forEach((child) {
widgets.add(
ListTile(
title: Text(child.name.toString()),
subtitle: Text('${child.amount}'),
onTap: () => _onChildTap(child),
trailing: GestureDetector(
onTap: () { setState(() { children.remove(child); }); },
child: Icon(Icons.delete)
),
)
);
});
return widgets;
}
}
I would really appreciate your help.

Answer 1

I believe your problem is here:
List<ParentModel> results = [];
results.add(ParentModel(id: 1, name: 'Parent 1', children: children));
results.add(ParentModel(id: 2, name: 'Parent 2', children: children));
results.add(ParentModel(id: 3, name: 'Parent 3', children: children));
You are creating multiple instances of ParentModel, but assigning same instance of children, so basically children are shared through 3 different parents, if you update children of one of these parents, all 3 parents will be updated in same way.