Design Patterns

clone_with_mirrors.dart

import 'dart:mirrors';

class A {
  late String a;

  A clone() {
    var instance = reflect(this);
    var newInstance = reflect(this).type.newInstance(
      Symbol.empty,
      []
    );
    ClassMirror? classMirror = reflectClass(runtimeType);
    while (classMirror != null) {
      var fields = classMirror.declarations.values.whereType<VariableMirror>();
      for (var field in fields) {
        newInstance
            .setField(
            field.simpleName,
            instance
                .getField(field.simpleName)
                .reflectee
        )
            .reflectee;
      }
      classMirror = classMirror.superclass;
    }
    return newInstance.reflectee as A;
  }
}

class B extends A {
  late String b;
}

class C extends A {
  late String c;

  @override
  String toString() {
    return "$a $c";
  }
}

void main(List<String> arguments) {
  C c = C();
  c.a = 'hello';
  c.c = 'world';
  print(c.clone());
}

cloner.dart

class A {
  late String a;
}

class B extends A {
  late String b;
}

class C extends A {
  late String c;

  @override
  String toString() {
    return "$a $c";
  }
}

abstract class Copier<T> {

  T convert(T t) {
    T newT = newInstance();
    setProperties(t, newT);
    return newT;
  }

  T newInstance();

  void setProperties(T obj, T newObj);
}

class ACopier extends Copier<A> {

  @override
  A newInstance() {
    return A();
  }

  @override
  void setProperties(A obj, A newObj) {
    newObj.a = obj.a;
  }
}

class BCopier extends ACopier {
  @override
  A newInstance() {
    return B();
  }

  @override
  void setProperties(A obj, A newObj) {
    (newObj as B).b = (obj as B).b;
    super.setProperties(obj, newObj);
  }
}

class CCopier extends ACopier {
  @override
  A newInstance() {
    return C();
  }

  @override
  void setProperties(A obj, A newObj) {
    (newObj as C).c = (obj as C).c;
    super.setProperties(obj, newObj);
  }
}

class Cloner {
  Map<Type, Copier> converters = {
    A: ACopier(),
    B: BCopier(),
    C: CCopier()
  };

  T clone<T>(T value) {
    return converters[value.runtimeType]?.convert(value);
  }
}

void main(List<String> arguments) {
  Cloner cloner = Cloner();
  C c = C();
  c.a = "hello";
  c.c = "world";
  print(cloner.clone(c));
}