How To Sort Nested ObjectData Flutter - sorting

Question

I am trying to sort a JSON object that has nested data. I want to refresh the List of object each time a button is pressed but, I am having issues doing so. I am trying to sort by price and this is my code so far:
Data:
{
"id": 152,
"name": "Advil",
"short_description": "Advil 20 Pack",
"usage": "Headaches",
"effect": "MoodSwings",
"sizes": [
{
"id": 307,
"size": 4,
"product_id": 152,
"price": 4.99
},
{
"id": 308,
"size": 5,
"product_id": 152,
"price": 12.66
}
],
}
My model is set up like this:
Product(
{this.id,
this.name,
this.shortDescription,
this.image,
this.image2,
this.image3,
this.type,
this.sizes,
this.usage,
this.filter,
this.category,
this.prodSize});
factory Product.fromJSON(Map<String, dynamic> json) {
var sizes = json['sizes'] as List;
print(sizes.runtimeType);
List<ProductSizes> sizeList =
sizes.map((i) => ProductSizes.fromJSON(i)).toList();
return Product(
id: json['id'],
name: json['name'],
shortDescription: json['short_description'],
image: json['image'],
image2: json['image2'],
image3: json['image3'],
type: json['Product_Type'],
sizes: sizeList,
usage: json['usage'],
filter: json['filter'],
category: json['Product_Category'],
);
}
}
class ProductSizes {
int id;
int size;
int productId;
double price;
ProductSizes({this.id, this.size, this.productId, this.price});
factory ProductSizes.fromJSON(Map<String, dynamic> json) {
return ProductSizes(
id: json['id'],
size: json['size'],
productId: json['product_id'],
price: json['price']);
}
}
My switch case that is tied to a dropdownbutton:
void _sortProductsDropDown(_filterDropdown, productList) {
var tempProducts;
setState(() {
switch (_filterDropdown) {
case 'Price: Low-High':
for (int i = 0; i < productList.length; i++) {
tempProducts.add(productList[i]
.sizes
.sort((a, b) => b.$price.reversed(a.price)));
}
_productTabFilter = tempProducts;
print(tempProducts.toString());
break;
case 'Price: High-Low':
print(_filterDropdown);
for (int i = 0; i < productList.length; i++) {
tempProducts.add(productList[i]
.sizes
.sort((a, b) => a.$price.compareTo(b.price)));
}
_productTabFilter = tempProducts;
print(tempProducts.toString());
break;
}
});
// return productList;
}
That is being called by the onchange method for the drop down button here:
void _changeFilterList(String value) {
//use _filterDropdown for switch statement
setState(() {
_filterDropdown = value;
});
print(' the value of the dropdown is $_filterDropdown');
_sortProductsDropDown(_filterDropdown, productList);
}
Then I use a gridview builder to make the data
return GridView.builder(
itemCount: _productTabFilter.length,
controller: ScrollController(),
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 2,
mainAxisSpacing: 20,
childAspectRatio: 0.7),
shrinkWrap: true,
scrollDirection: Axis.vertical,
itemBuilder: (context, i) {
Then it throws this error:
[VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception: type '(dynamic, dynamic) => dynamic' is not a subtype of type '(ProductSizes, ProductSizes) => int' of 'compare'
Any help would be appreciated

Answer 1

Try casting that object to a List and then use the sort function on that list.
like this:
(productList[i]['sizes'] as List).sort((a, b) => a['price'].compareTo(b['price']))