Chain of resposability

chain_of_responsability.dart

abstract class Validator {
  final Validator? nextValidator;

  Validator([this.nextValidator]);

  bool call(int value);
}

class Class1 implements Validator {
  @override
  final Validator? nextValidator;

  Class1([this.nextValidator]);

  @override
  bool call(int value) {
    if (nextValidator != null) {
      if (value >= 10) {
        return nextValidator!(value);
      }

      throw Exception('Error on class 1 with value $value');
    }

    return value >= 10
        ? true
        : throw Exception('Error on class 1 with value $value');
  }
}

class Class2 implements Validator {
  @override
  final Validator? nextValidator;

  Class2([this.nextValidator]);

  @override
  bool call(int value) {
    if (nextValidator != null) {
      if (value >= 100) {
        return nextValidator!(value);
      }

      throw Exception('Error on class 2 with value $value');
    }

    return value >= 100
        ? true
        : throw Exception('Error on class 2 with value $value');
  }
}

class Class3 implements Validator {
  @override
  final Validator? nextValidator;

  Class3([this.nextValidator]);

  @override
  bool call(int value) {
    if (nextValidator != null) {
      if (value >= 1000) {
        return nextValidator!(value);
      }

      throw Exception('Error on class 3 with value $value');
    }

    return value >= 1000
        ? true
        : throw Exception('Error on class 3 with value $value');
  }
}

void main() {
  const value = 2000;
  final v3 = Class3();
  final v2 = Class2(v3);
  final v1 = Class1(v2);

  print(v1(value));
}