如何解析flutter中的map Json列表？

I have one Json structure with three maps, one is list of products then total and tax. I have to parse this json structure in flutter. I created on model class. Now i am getting the error in type casting.

怎么解决这个问题呢？

JSON 结构：

{
  "products" : [
     {                  
       "cart_id": "7",      
     },          
     {                  
       "cart_id": "7",
     }     
  ],
  "total": 100,
  "tax": 100
}

型号类别：

class CartModel {   
    List<Product> produtcts;
    double total;

    CartModel({this.produtcts, this.total});

    factory CartModel.fromJson(Map<String, dynamic> json) {
        var list = json['products'] as List;
        print(list.runtimeType);
        List<Product> products = list.map((i) => 
           Product.fromJson(i)).toList();

        return CartModel(
            produtcts: products, total: json['total'],);
    }
}

class Product {
    String cartId;

    Product({this.cartId,});

    factory Product.fromJson(Map<String, dynamic> json) {
        return Product(     
            productId: json['cart_id'],
        );
    }
}

不要将产品数组转换为列表，而是尝试将其用作Iterable.

对我来说，以下代码有效（请注意json.decode(String)方法是从导入的dart:convert包裹）：

var data = '{"products":[{"cart_id": "7"},{ "cart_id": "7"}], "total": 100, "tax": 100}';
var decoded = json.decode(data);   
var cartModel = CartModel.fromJson(decoded);

class CartModel {   
    List<Product> produtcts;
    int total;

    CartModel({this.produtcts, this.total});

    factory CartModel.fromJson(Map<String, dynamic> json) {
        Iterable list = json['products'];
        print(list.runtimeType);
        List<Product> products = list.map((i) => 
           Product.fromJson(i)).toList();

        return CartModel(
            produtcts: products, total: json['total'],);
    }
}

class Product {
    String productId;

    Product({this.productId,});

    factory Product.fromJson(Map<String, dynamic> json) {
        return Product(     
            productId: json['cart_id'],
        );
    }
}