How can I extract uniqued caterogies from JSON in Flutter? - json

Question

I have a JSON
[{"id":495, "title":"BSB", "category":null},{"id":495, "title":"BCB", "category":"temp"},{"id":495, "title":"BSB", "category":"temp"},{"id":495, "title":"BSB", "category":"cat12"},...]
I want to extract uniqued categories in a list without contain null value in Flutter. Example: List ["temp","cat12"...]
How to use model to fetch the categories from JSON?
Thanks in advance.
My current model.dart:
List<Product> productFromJson(String str) => List<Product>.from(json.decode(str).map((x) => Product.fromJson(x)));
String productToJson(List<Product> data) => json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
class Product {
Product({
this.id,
this.title,
this.category,
});
int id;
String title;
String category;
factory Product.fromJson(Map<String, dynamic> json) => Product(
id: json["id"],
title: json["title"],
category: json["category"] == null ? null : json["category"],
);
Map<String, dynamic> toJson() => {
"id": id,
"title": title,
"category": category == null ? null : category,
};
}

Answer 1

// #dart=2.12
void doSomething() {
var list = [{"id":495, "title":"BSB", "category":null},{"id":495, "title":"BCB", "category":"temp"},{"id":495, "title":"BSB", "category":"temp"},{"id":495, "title":"BSB", "category":"cat12"}];
var myList = list.map((m) => m['category']).toSet().where((e) => e != null);
print(myList);
}
void main() {
doSomething();
}
Result:
(temp, cat12)