Reorder Array of objects Flutter - flutter

Question

Array of object
Input:
[
{id:1,order:1},
{id:2,order:null},
{id:3,order:0},
{id:4,order:null},
{id:5,order:3}
]
Output:
[
{id:3,order:0},
{id:1,order:1},
{id:2,order:null},
{id:5,order:3},
{id:4,order:null}
]
Considering model
Item(int id,int? Order)
By default the order is null and these positions are to be maintained and object having orders are to be moved up or down.

Answer 1

Try this, if the array is of type Map -
arrayOfObjects.sort((a, b) => a['order'].compareTo(b['order']));
Or this if it is holding Item class with an order attribute
arrayOfObjects.sort((Item a, Item b) => a.order.compareTo(b.order));
Note - You can remove items with null order before running the sort.
Example
arrayOfObjects.removeWhere((item)=> item.order == null);

Answer 2

The double Iterations are based on the length of the array to handle the nulls.
Solution
import 'package:collection/collection.dart';
class Item {
int? _id;
int? _order;
Item({int? id, int? order}) {
this._id = id;
this._order = order;
}
int? get id => _id;
set id(int? id) => _id = id;
int? get order => _order;
set order(int? order) => _order = order;
Item.fromJson(Map<String, dynamic> json) {
_id = json['id'];
_order = json['order'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['id'] = this._id;
data['order'] = this._order;
return data;
}
}
List<Item> reorder(List<Item> it){
var tempData = it;
tempData.forEach((_){
tempData.forEachIndexed((index,val){
///Remove original and replace
var ind = val.order;
if(ind!=null){
///Check if it is at the Proper Position
if (index == ind) {
return;
}
var first = it.removeAt(index);
it.insert(ind as int, first);
}
});
});
return it;
}
void main() {
var list = [
Item(id: 1, order: 1),
Item(id: 3, order: 2),
Item(id: 2, order: 7),
Item(id: 4, order: null),
Item(id: 5, order: null),
Item(id: 6, order: null),
Item(id: 7, order: 6),
Item(id: 8, order: 4)
];
list.forEach((it) => print('${it.id} ->${it.order}'));
var first = reorder(list);
print('\n');
first.forEach((it) => print('${it.id} ->${it.order}'));
///Stack List
}