How to create a model in flutter - flutter

Question

I'm watching the old flutter course because I couldn't really find a new one. But since flutter is constantly updated, it becomes a little more challenging as soon as you learn from the old courses.
Here is my questions:
Is fromObject still here or just changed to fromJson?
Do you have a model sample?
How can I do my _id is unique?(Usin sql etc.)
I'm trying something like this but I'm getting an error in 'Product.fromObject'.
class Product {
int _id;
String _name;
String _description;
double _price;
Product(this._id, this._name, this._description, this._price);
Product.withId(this._id, this._name, this._description, this._price);
int get id => _id;
String get name => _name;
String get description => _description;
double get price => _price;
set name(String value) {
if (value.length >= 2) {
_name = value;
}
}
set description(String value) {
if (value.length >= 10) {
_description = value;
}
}
set price(double value) {
if (value > 0) {
_price = value;
}
}
Map<String, dynamic> toMap() {
var map = <String, dynamic>{};
map["name"] = _name;
map["description"] = _description;
map["price"] = _price;
map["id"] = _id;
return map;
}
Product.fromObject(dynamic o) {
_id = o["id"];
_name = o["name"];
_description = o["description"];
_price = o["price"];
}
}```

Answer 1

Now It's changed to fromJson.
class Post{
int userid;
int id;
String title;
String body;
Post({userid, id, title, body});
Post fromJson(Map<String, dynamic> json){
Post post = Post();
post.userid = json["userId"];
post.id = json['id'];
post.title = json['title'];
post.body = json['body'];
return post;
}
Map<String, dynamic> toJson(Post post){
Map<String, dynamic> data = {
"userId": post.userid,
"id": post.id,
"title": post.title,
"body": post.body
};
return data;
}
}
I have attached a sample model class for your reference.

Answer 2

You can read about json serialization here: https://flutter.dev/docs/development/data-and-backend/json
The correct method to parse from json is a factory method that is called fromJson and takes a map.