I’m working on a Flutter application where I’m trying to send a POST request to a Node.js server to add a product. However, I’m encountering an issue where the server responds with a “Product is not a constructor” error. Here’s the setup:

admin_services.dart

import 'dart:convert';
import 'dart:io';

import 'package:cloudinary_public/cloudinary_public.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:provider/provider.dart';
import 'package:swadesh/constants/errors.dart';
import 'package:swadesh/constants/global_variables.dart';
import 'package:swadesh/constants/utils.dart';
import 'package:swadesh/models/product.dart';
import 'package:swadesh/providers/user_provider.dart';

class AdminServices {
  void sellProduct({
    required BuildContext context,
    required String name,
    required String description,
    required double price,
    required double quantity,
    required String category,
    required List<File> images,
  }) async {
    final userProvider = Provider.of<UserProvider>(context, listen: false);

    try {
      final cloudinary = CloudinaryPublic('dypdblusf', 'pmfi2yqj');
      List<String> imageUrls = [];

      // Upload images to Cloudinary and collect URLs
      for (int i = 0; i < images.length; i++) {
        CloudinaryResponse res = await cloudinary.uploadFile(
          CloudinaryFile.fromFile(images[i].path, folder: name),
        );
        imageUrls.add(res.secureUrl);
      }

      // Create product object
      Product product = Product(
        name: name,
        description: description,
        quantity: quantity,
        images: imageUrls,
        category: category,
        price: price,
      );

      // Convert product object to JSON
      String jsonBody = json.encode(product.toMap());

      // Send HTTP POST request to server
      http.Response res = await http.post(
        Uri.parse('$uri/admin/add-product'),
        headers: {
          'Content-Type': 'application/json; charset=UTF-8',
          'x-auth-token': userProvider.user.token,
        },
        body: jsonBody,
      );

      // Handle the response
      httpErrorHandle(
        response: res,
        context: context,
        onSuccess: () {
          showSnackBar(context, 'Product Added Successfully!');
          Navigator.pop(context);
        },
      );
    } catch (e) {
      showSnackBar(context, e.toString());
    }
  }
}

product.dart

import 'dart:convert';

class Product {
  final String name;
  final String description;
  final double quantity;
  final List<String> images;
  final String category;
  final double price;

  Product({
    required this.name,
    required this.description,
    required this.quantity,
    required this.images,
    required this.category,
    required this.price,
  });

  Map<String, dynamic> toMap() {
    return <String, dynamic>{
      'name': name,
      'description': description,
      'quantity': quantity,
      'images': images,
      'category': category,
      'price': price,
    };
  }

  factory Product.fromMap(Map<String, dynamic> map) {
    return Product(
      name: map['name'],
      description: map['description'],
      quantity: map['quantity'].toDouble(),
      images: List<String>.from(map['images']),
      category: map['category'],
      price: map['price'].toDouble(),
    );
  }

  String toJson() => json.encode(toMap());

  factory Product.fromJson(String source) =>
      Product.fromMap(json.decode(source));
}

When I run this code, the server responds with:

{
  "error": "Product is not a constructor"
}

I’ve checked that the Product model is correctly defined and imported in my server-side code.
The JSON payload sent from Dart looks like this: {“name”:”Product Name”,”description”:”Product Description”,”quantity”:10,”images”:[“url1″,”url2″,”url3″],”category”:”Category Name”,”price”:99.99}.
The Product class in Dart is structured to match the expected structure on the Node.js server.

What could be causing this issue and how can I resolve it? Any help would be appreciated. Thank you!