Factory Constructor in my understanding

factory_constructor.txt

//The user factory constructor, when called will return the same instance, no matter how many times. Hence, the name singleton.

main(){
  var user1 = User();
  user1.name = "Mike";
  user1.age = 3;
  var user2 = User();
  print([user1, user2]);
}

class User{
  String name;
  int age;
  static final User _singleton = User._internal();

// There is a _singleton property that contructs the user class using the internal named constructor.
//This action is done once. As you see, the _singleton is a final property.
// Its value does not change. 
//Anytime it is called upon, it just returns the constructed user object that was constructed using the named construtor(_internal).

  factory User(){
    return _singleton;
  }
  
  // So, whenever the factory User() constructor is called upon, it returns the _singleton object.
  //Of course, this returns the User object that was initially created at the beginning.
  
  
  User._internal();

// This is a valid constructor.
// It is as good as calling User().
  
  @override
  String toString() {
    return 'User{name: $name, age: $age}';
  }
}

// Therefore, anytime we call User() constructor, we are actually calling the factory constructor, which returns the _singleton object.
// Which has a value of a constructed User object.
//Call User() as many times as you like, you get the same object returned to you!