In Dart, is it possible to pass an argument in a singleton?

class Peoples {
  late int id;
  late String name;

  static final Peoples _inst = Peoples._internal();

  Peoples._internal();

  factory Peoples() {
    return _inst;
  }
}

I have this singleton class. Which ensures that, only one instance of a class is ever created. So, even if someone tries to instantiate it, they will use the same instance. And i can create and set values, like:

  Peoples ps1 = Peoples();
  Peoples ps2 = Peoples();

  ps1.id = 1;
  ps1.name = "First";

  ps2.id = 2;
  ps2.name = "Second";

Is it possible to instantiate and set values like:

  Peoples ps1 = Peoples(1, "First");
  Peoples ps2 = Peoples(2, "Second");

So, now both "ps1" and "ps2" will have (2, "Second").

Sure! You need to pass the arguments to the factory method then you need to update the properties USING the referenced instance.

For example, you had

class Peoples {
  late int id;
  late String name;

  static final Peoples _inst = Peoples._internal();

  Peoples._internal();

  factory Peoples() {
    return _inst;
  }
}

If you apply my solution then you have

class Peoples {
  late int id;
  late String name;

  static final Peoples _inst = Peoples._internal();

  Peoples._internal();

  factory Peoples({int id, String name}) {
    _inst.id = id
    _inst.name = name
    return _inst;
  }
}

with this your question should be answered for more info about factory and params visit

https://dart.dev/guides/language/language-tour

Working Example

class Peoples {
  late int id;
  late String name;

  static final Peoples _inst = Peoples._internal();

  Peoples._internal();
  

  factory Peoples(int id, String name) {
    _inst.id = id;
    _inst.name = name;
    return _inst;
  }
}

void main() {
  print("Instance of = " + Peoples(0, "Dylan").name);
  print("Instance of = " + Peoples(1, "Joe").name);
  print("Instance of = " + Peoples(2, "Maria").name);
}