How do I use a StreamProvider from a StateNotifierProvider?

Question

I am try to use a StreamProvider from a StateNotifierProvider.

Here is my StreamProvider, which works fine so far.

final productListStreamProvider = StreamProvider.autoDispose<List<ProductModel>>((ref) {
  CollectionReference ref = FirebaseFirestore.instance.collection('products');
  return ref.snapshots().map((snapshot) {
    final list = snapshot.docs
        .map((document) => ProductModel.fromSnapshot(document))
        .toList();
    return list;
  });
});

Now I am trying to populate my shopping cart to have all the products in it from scratch.

final cartRiverpodProvider = StateNotifierProvider((ref) => 
new CartRiverpod(ref.watch(productListStreamProvider));

This is my CartRiverPod StateNotifier

class CartRiverpod extends StateNotifier<List<CartItemModel>> {

  CartRiverpod([List<CartItemModel> products]) : super(products ?? []);

  void add(ProductModel product) {
    state = [...state, new CartItemModel(product:product)];
    print ("added");
  }

  void remove(String id) {
    state = state.where((product) => product.id != id).toList();
  }
}

Solution

The simplest way to accomplish this is to accept a Reader as a parameter to your StateNotifier.

For example:

class CartRiverpod extends StateNotifier<List<CartItemModel>> {
  CartRiverpod(this._read, [List<CartItemModel> products]) : super(products ?? []) {
    // use _read anywhere in your StateNotifier to access any providers.
    // e.g. _read(productListStreamProvider);
  }

  final Reader _read;

  void add(ProductModel product) {
    state = [...state, new CartItemModel(product: product)];
    print("added");
  }

  void remove(String id) {
    state = state.where((product) => product.id != id).toList();
  }
}

final cartRiverpodProvider = StateNotifierProvider<CartRiverpod>((ref) => CartRiverpod(ref.read, []));

Comments

[Rahul Denmoto]

Alex, thank you so much! That's exactly what I was looking for.

[Alex Hartford]

@RahulDenmoto You're welcome. Please mark the answer as accepted to aid future readers. Glad it worked out for you!