flutter - Declare a variable to store an object that is only constructed with a specific named constructor in dart

Question

    class ExampleClass {
      //default constructor
      ExampleClass() {
        //do stuff
      }
      //named constructor
      ExampleClass.namedConstructor() {
        //do stuff
      }
    }
    void main() {
     //is there a way to create a variable with datatype to store an object that is constructed only with a specific constructor?

//I have tried something like this, but it returns an error
         ExampleClass.namedConstructor variable_1;
    }

Is there any way to do this or an alternative? because I need to be able to differentiate between an object that is constructed with the default constructor or with a named constructor.

question from:https://stackoverflow.com/questions/65937866/declare-a-variable-to-store-an-object-that-is-only-constructed-with-a-specific-n

Answer 1

You can add some identification to classes builded with different constructors and compare entities by unique parameters.

If instances of your classes creating once (Singleton design pattern), you can create entities as constants and compare it by reference:

const administrator = User.administrator();

class User {
  final int id;

  User(this.id);

  factory User.administrator() {
    return User(0);
  }

  factory User.administrator(int id) {
    return User(id);
  }
}