Flutter class in class to json decode - json

Question

How can I use class in class value?
For example I have a class like below.
import 'dart:convert';
class Product {
final String productId;
final String productName;
final String productImageUrl;
final String productCategory;
Product(
{required this.productId,
required this.productName,
required this.productImageUrl,
required this.productCategory});
factory Product.fromJson(Map<String, dynamic> json) {
return Product(
productId: json['productId'],
productName: json['productName'],
productImageUrl: json['productImageUrl'],
productCategory: json['productCategory'],
);
}
static Map<String, dynamic> toMap(Product product) => {
'productId': product.productId,
'productName': product.productName,
'productImageUrl': product.productImageUrl,
'productCategory': product.productCategory,
};
static String encode(List<Product> products) => json.encode(
products
.map<Map<String, dynamic>>((product) => Product.toMap(product))
.toList(),
);
static List<Product> decode(String products) =>
(json.decode(products) as List<dynamic>)
.map<Product>((item) => Product.fromJson(item))
.toList();
}
And I can use encode and decode like this.
Encode:
final String encodedData = Product.encode([
Product(
productId: "1",
productName: "Americano",
productImageUrl: "assets/americano.jpeg",
productCategory: "Warm"),
Product(
productId: "2",
productName: "Latte",
productImageUrl: "assets/americano.jpeg",
productCategory: "Cold"),
]);
Decode:
List<Product> products;
products = Product.decode(encodedData);
Now here is my question. If I want to use this product class like list in another class. How can I write encode, decode and fromJson methods? Can you help me? And please give me example usages.
import 'dart:convert';
import 'package:orderapp/models/product.dart';
class Bill {
final String billNo;
final String billNumber;
final String tableNo;
final String orderDateTime;
final String orderWaiter;
final List<Product> products;
Bill({
required this.billNo,
required this.billNumber,
required this.tableNo,
required this.orderDateTime,
required this.orderWaiter,
required this.products,
});
}

Answer 1

The data class with JSON decoder and encoder support.
import 'dart:convert';
class Product {
final String productId;
final String productName;
final String productImageUrl;
final String productCategory;
Product({
required this.productId,
required this.productName,
required this.productImageUrl,
required this.productCategory,
});
Map<String, dynamic> toMap() => {
'productId': productId,
'productName': productName,
'productImageUrl': productImageUrl,
'productCategory': productCategory,
};
factory Product.fromMap(Map<String, dynamic> map) => Product(
productId: map['productId'] as String,
productName: map['productName'] as String,
productImageUrl: map['productImageUrl'] as String,
productCategory: map['productCategory'] as String,
);
String toJson() => json.encode(toMap());
factory Product.fromJson(String source) {
return Product.fromMap(json.decode(source) as Map<String, dynamic>);
}
}