Bad state : no element

Question

I'm getting this error while going through a list , the thing is the list isn't null since i have some manual data put it so i'm not sure what am i doing wrong , here is my code

class ProductDetailScreen extends StatelessWidget {
  // final String title;
  // final double price;

  // ProductDetailScreen(this.title, this.price);
  static const routeName = '/product-detail';

  @override
  Widget build(BuildContext context) {
    final String productId =
        ModalRoute.of(context).settings.arguments as String; // is the id!

    final loadedProduct = Provider.of<Products>(
      context,
      listen: false,
    ).findById(productId);

    // ...
    return Scaffold(
      appBar: AppBar(
        title: Text(loadedProduct.title),
      ),
    );
  }
}

the find by view id method is from here :

    import 'package:flutter/material.dart';
import 'package:shop_app/providers/product.dart';

class Products with ChangeNotifier {
  List<Product> _items = [
    Product(
      id: 'p1',
      title: 'Red Shirt',
      description: 'A red shirt - it is pretty red!',
      price: 29.99,
      imageUrl:
          'https://cdn.pixabay.com/photo/2016/10/02/22/17/red-t-shirt-1710578_1280.jpg',
    ),
    Product(
      id: 'p2',
      title: 'Trousers',
      description: 'A nice pair of trousers.',
      price: 59.99,
      imageUrl:
          'https://upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Trousers%2C_dress_%28AM_1960.022-8%29.jpg/512px-Trousers%2C_dress_%28AM_1960.022-8%29.jpg',
    ),
    Product(
      id: 'p3',
      title: 'Yellow Scarf',
      description: 'Warm and cozy - exactly what you need for the winter.',
      price: 19.99,
      imageUrl:
          'https://live.staticflickr.com/4043/4438260868_cc79b3369d_z.jpg',
    ),
    Product(
      id: 'p4',
      title: 'A Pan',
      description: 'Prepare any meal you want.',
      price: 49.99,
      imageUrl:
          'https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Cast-Iron-Pan.jpg/1024px-Cast-Iron-Pan.jpg',
    ),
  ];

  List<Product> get items {
    return [..._items];
  }

  Product findById(String id) {
    return _items.firstWhere((prod) => prod.id == id);
  }

  void addProduct() {
    notifyListeners();
  }
}

any idea why it wouldn't work ? i have the dummy data added already so it should be scanning that list shouldn't it ?

Answer 1

firstWhere returns the first element that satisfies the given predicate test.

If no element satisfies test, the result of invoking the orElse function is returned. If orElse is omitted, it defaults to throwing a StateError.