Flutter Getx – Updating item in children list is not reactive

Issue

When I add an item to the obs sublist, the widget is not updating.
If I add an item to the main list, it’s working fine.

Please help me to properly implement reactive.

home_controller.dart

import 'package:get/get.dart';

class FoodCategory {
  final String name;
  final List<String> foods;
  FoodCategory({required this.name, required this.foods});
}

class HomeController extends GetxController {
  late final List<FoodCategory> foodList;

  @override
  void onInit() {
    super.onInit();
    foodList = [
      FoodCategory(name: "Fruits", foods: ["Apple", "Orange"]),
      FoodCategory(name: "Vegetable", foods: ["Carrot", "Beans"])
    ].obs;
  }

  void addFood(index, food) {
    foodList[index].foods.add(food);  // Not Working. Item added but UI not re-rendered.
    print(food + " added");
  }

  void addCategory(FoodCategory foodcategory) {
    foodList.add(foodcategory);  // Working Fine.
    print("New food category added");
  }
}

home_view.dart

class HomeView extends GetView<HomeController> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Example"),
      ),
      body: Container(
        child: Obx(
          () => Column(
            children: [
              for (var foodCat in controller.foodList)
                Container(
                  width: 300,
                  height: 100,
                  child: Row(
                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text(foodCat.name),
                      Column(
                        children: [for (var food in foodCat.foods) Text(food)],
                      ),
                      TextButton(
                          onPressed: () => controller.addFood(0, "Banana"), // Not Working
                          child: Text("Add Food")) 
                    ],
                  ),
                )
            ],
          ),
        ),
      ),
      floatingActionButton: FloatingActionButton(
          child: Text("Add Category"),
          onPressed: () => controller
              .addCategory(FoodCategory(name: "pulse", foods: ["wheat"]))), // Working.
    );
  }
}

enter image description here

Solution

I finally figured out.

Converting List to RxList and using refresh() do the magic.

Change

late final List<FoodCategory> foodList; 

into

late final RxList<FoodCategory> foodList; 

After updating the item, add Your_RxList_Variable.refresh().

void addFood(index, food) {
    foodList[index].foods.add(food);
    foodList.refresh();
}

Answered By – rajagopalx

Answer Checked By – Cary Denson (FlutterFixes Admin)

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