How Can I Clone a Map List to Another Map List?

Question

My map list on another list and I use switch case in my main page I need to transfer my list to a new list but I can't. As you can see there is a 'lastproduct' and it is a string I made a questioning and tried to make transfer a map list to another new one. It doesn't work. Is there a any mistake?

import 'package:floria/scripts/gridviewcustom.dart';
import 'package:floria/scripts/productlist.dart';
import 'package:flutter/material.dart';

class PurchasingPage extends StatefulWidget {
  PurchasingPage(this.lastproduct, {Key? key}) : super(key: key);

  final String lastproduct;
  List<Map<String, String>> lastname = [];

  @override
  identifyproductname(lastproduct) {
    switch (lastproduct) {
      case 'Zambak':
        return lastname.addAll(gerbera);
      case 'Gül':
        return lastname.addAll(rose);
      case 'Papatya':
        return lastname.addAll(daisy);
      case 'Şakayık':
        return lastname.addAll(peony);
    }
  }

  void initState() {
    identifyproductname(lastproduct);
  }

  State<PurchasingPage> createState() => _PurchasingPageState();
}

class _PurchasingPageState extends State<PurchasingPage> {
  int optionSelected = 0;

  void checkOption(int index) {
    setState(() {
      optionSelected = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      appBar: AppBar(
        flexibleSpace: Container(
          decoration:
              BoxDecoration(gradient: LinearGradient(begin: Alignment.topCenter, end: Alignment.bottomCenter, colors: [Theme.of(context).primaryColor, Theme.of(context).secondaryHeaderColor])),
        ),
        title: Container(
            width: 90,
            height: 45,
            child: Image.asset(
              "assets/images/floria.png",
              fit: BoxFit.fill,
            )),
        centerTitle: true,
      ),
      body: Center(
        child: GridView.count(
          crossAxisCount: 2,
          mainAxisSpacing: 5,
          crossAxisSpacing: 5,
          children: [
            for (var i = 0; i <  widget.lastname.length ; i++)
              GridViewCustom(
                productname: widget.lastname[i]['Productname'] as String,
                img: widget.lastname[i]['img'] as String,
                onTap: () => checkOption(i + 1),
                selected: i + 1 == optionSelected,
              )
          ],
        ),
      ),
    );
  }
}

As you can see there is a 'lastproduct' and it is string I wanna make a questioning and

Answer 1

Not really understand what you try to add with rose, daisy.. But here I have created an extension that always returns a new list, work event with immutable lists.

import 'package:flutter/foundation.dart';

void main() {
  const a = <Map<String, Object>>[
    {'a': 'A'},
    {'b': 'B'},
    {'c': 'C'},
  ];
  
  const b = <Map<String, Object>>[
    {'b': 'B'},
  ];
  
  print(a + b); // [{a: A}, {b: B}, {c: C}, {b: B}]
  print(a - b); // [{a: A}, {c: C}]
}

extension on Iterable<Map<String, Object>> {
  Iterable<Map<String, Object>> operator +(List<Map<String, Object>> other) {
    return followedBy(other);
  }

  Iterable<Map<String, Object>> operator -(List<Map<String, Object>> other) {
    return where((a) => !other.any((b) => mapEquals(a, b))).toList();
  }
}