Question 75760 in Flutter Question posted in
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Error cart provider parsing int to type 'num' – Flutter

I have an error inside my project
total += double.parse(value.price!) * value.quantity;
in this line, the error occurs

The argument type ‘int?’ can’t be assigned to the parameter type
‘num’.

cart_provider.dart

import 'package:flutter/foundation.dart';
import 'package:myproject/model/CartModel.dart';

class Cart with ChangeNotifier {
  Map<String, CartModel> _items = {};

  Map<String, CartModel> get items {
    return {..._items};
  }
  

  void addItem({required String productId,price,title,name,image,quantity}){
    if(_items.containsKey(productId)){
      _items.update(productId, (value) => CartModel(
        key: value.key,
        name:value.name,
        image:value.image,
        price:value.price,
        quantity:value.quantity! + 1,
        totalPrice:value.totalPrice,

      ));
      notifyListeners();

    }else{
      _items.putIfAbsent(productId, () => CartModel(
        key:DateTime.now().toString(),
        name:name,
        image:image,
        price:price,
        totalPrice:0,
        quantity: 1,

      ));
      notifyListeners();

    };
  }
  
    double get totalToPay{  
      double total = 0.0;
      _items.forEach((key, value) {
        total += double.parse(value.price!) * value.quantity;
      });
      return total;
    }
}

Here is my cartModel.dart

class CartModel {
  String? key;
  String? name;
  String? image;
  String? price;
  int? quantity;
  double? totalPrice;

  CartModel(
      {required this.key,
      required this.name,
      required this.image,
      required this.price,
      required this.quantity,
      required this.totalPrice});

  CartModel.fromJson(Map<String, dynamic> json) {
    key = json['key'];
    name = json['name'];
    image = json['image'];
    price = json['price'];
    quantity = json['quantity'] as int;
    totalPrice = double.parse(json['totalPrice']);
  }

  Map<String,dynamic> toJson(){
    final Map<String,dynamic> data = new Map<String,dynamic>();
    data['key'] = this.key;
    data['name'] = this.name;
    data['image'] = this.image;
    data['price'] = this.price;
    data['quantity'] = this.quantity;
    data['totalPrice'] = this.totalPrice;

    return data;
  }

}
Tags:

2

Answers


  1. 0

    In your CartModel int? quantity is nullable, so you have to use a null check on value.quantity.
    Try

    total += double.parse(value.price!) * value.quantity!; // extra exclamation point here
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  2. 0

    value.quantity can get null and using null-assert (!) have some risk. Also a better way of parsing double from string will be using .tryParse which handle exception.

     total += double.tryParse("${value.price}") ?? 0 * (value.quantity ?? 0);
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