How to make a Model Class Within Model Class (Flutter / Dart) - firebase

Question

I am trying to make a multivendor app with Flutter.
The problem I am facing right now is how can I make a model class within a Model class:
Example:
class ProductModel {
String? name;
double? price;
String? imgUrl;
double? weight;
ProductModel();
ProductMode.fromSnapShot(DocumentSnapshot snapshot){
name = snapshot['name'];
price= snapshot['price'];
imgUrl= snapshot['imgUrl'];
weight= snapshot['weight'];
}
}
I have already retrieved all the products from Firestore:
class VendorModel{
String? name;
String? imgUrl;
DateTime? opensAt;
DateTime? closesAt;
VendorModel();
VendorModel.fromSnapshot(DocumentSnapshot snapshot){
name = snapshot['name'];
imgUrl= snapshot['imgUrl'];
opensAt= DateTime.tryParse(snapshot['opensAt'].toString());
closesAt= DateTime.tryParse(snapshot['closesAt'].toString());
}
}
I have also retrieved all the vendors from Firestore:
Here is What I am trying to do:
I would like to add the products I fetched from Firestore to their respective vendors using this model. But I don't know how to make this if my data is from Firestore.
class VendorWithProductsModel{
VendorModel vendor;
List<ProductModel> products;
VendorWithProductsModel();
(I AM STUCK HERE)
}
Here is a Snippet of my Firestore code in retrieving products and vendors:
VendorModel _vendor = VendorModel();
List<VendorModel> _allVendors = [];
Future<VendorModel> getCertainVendor(docId) async{
await vendor.doc(docId).get().then((value){
_vendor = VendorModel.fromSnapshot(value);
});
return _vendor;
}
Future<List<VendorModel>> getAllVendors() async{
await vendor.get().then((value){
_allVendors.add(VendorModel.fromSnapshot(value));
});
return _allVendors;
}

Answer 1

In your product model, you need something like vendorId, where you can know which product belongs to which vendor.
After fetching all your products and vendors. Use both list, and loop through them, this is pseudo code for example:
List<VendorWithProductsModel> doMagic (List<ProductModel> productList, List<VendorModel> vendorList) {
List<VendorWithProductsModel> vendorsWithProducts =[];
vendorList.forEach((vendor){
VendorWithProductsModel _vendorAndProduct = VendorWithProductsModel();
_vendorAndProduct.vendor = vendor;
_vendorAndProduct.products =[];
_vendorAndProduct.products = productList.where((e)=> e.vendorId == vendor.id).toList();
vendorsWithProducts.add(_vendorAndProduct);
});
return vendorsWithProducts;
}