What is an equivalent for Dart 2 to `typeof` of TypeScript? - dart

Question

I'm new to Dart 2. I want a class to have a property. It's a reference of other class. it's not an instance but class itself. In TypeScript, it's possible to write as below. Is there a same way in Dart 2?
class Item { }
class ItemList {
itemClass: typeof Item;
}
const itemList = new ItemList();
itemList.itemClass = Item;
UPDATED:
I added some more context. The following is minimal sample code. I want to delegate a role of instantiation to super class.
class RecordBase {
id = Math.random();
toJson() {
return { "id": this.id };
};
}
class DbBase {
recordClass: typeof RecordBase;
create() {
const record = new this.recordClass();
const json = record.toJson();
console.log(json);
}
}
class CategoryRecord extends RecordBase {
toJson() {
return { "category": "xxxx", ...super.toJson() };
};
}
class TagRecord extends RecordBase {
toJson() {
return { "tag": "yyyy", ...super.toJson() };
};
}
class CategoryDb extends DbBase {
recordClass = CategoryRecord;
}
class TagDb extends DbBase {
recordClass = TagRecord;
}
const categoryDb = new CategoryDb();
categoryDb.create();
const tagDb = new TagDb();
tagDb.create();

Answer 1

I have tried to make you sample code into Dart. As I told before, you cannot get a reference to a class and call the constructor on runtime based on this reference.
But you can make a reference to a method which constructs the object of you class.
import 'dart:math';
class RecordBase {
static final Random _rnd = Random();
final int id = _rnd.nextInt(100000);
Map<String, dynamic> toJson() => <String, dynamic>{'id': id};
}
abstract class DbBase {
final RecordBase Function() getRecordClass;
RecordBase record;
Map<String, dynamic> json;
DbBase(this.getRecordClass);
void create() {
record = getRecordClass();
json = record.toJson();
print(json);
}
}
class CategoryRecord extends RecordBase {
#override
Map<String, dynamic> toJson() {
return <String, dynamic>{'category': 'xxxx', ...super.toJson()};
}
}
class TagRecord extends RecordBase {
#override
Map<String, dynamic> toJson() {
return <String, dynamic>{'tag': 'yyyy', ...super.toJson()};
}
}
class CategoryDb extends DbBase {
CategoryDb() : super(() => CategoryRecord());
}
class TagDb extends DbBase {
TagDb() : super(() => TagRecord());
}
void main() {
final categoryDb = CategoryDb();
categoryDb.create(); // {category: xxxx, id: 42369}
final tagDb = TagDb();
tagDb.create(); // {tag: yyyy, id: 97809}
}
I am not really sure if the create() method should be seen as a method or a constructor. So I choose to make it a method to be closer to your code.