conflict_handler.dart

class Model {}

class ConflictData<M extends Model> {
  final M local;
  final M remote;

  const ConflictData(this.local, this.remote);
}

class ModelA extends Model {}

class ModelB extends Model {}

typedef ConflictHandler<M extends Model> = M Function(ConflictData<M>);

final Map<Type, ConflictHandler> handlers = {};

void registerConflictHandler<M extends Model>(ConflictHandler<M> handler) {
  handlers[M] = (ConflictData<Model> data) {
    return handler(ConflictData<M>(data.local as M, data.remote as M));
  };
}

void callConflictHandler(Type type, ConflictData data) {
  handlers[type]!(data);
}

void main() {
  registerConflictHandler((ConflictData<ModelA> conflictDataA) {
    print('Conflicting A values');
    return conflictDataA.local;
  });

  registerConflictHandler((ConflictData<ModelB> conflictDataB) {
    print('Conflicting B values');
    return conflictDataB.remote;
  });

  callConflictHandler(ModelA, ConflictData<ModelA>(ModelA(), ModelA()));
  callConflictHandler(ModelB, ConflictData<ModelB>(ModelB(), ModelB()));
}