Dart check nullable Type

Question

I looking to find a way to check if the type is nullable using switch statement but I got an error by doing that. Doesn't anyone know how to check if the type of object in the nullable state?

void dataFactory(Type type, data){
    switch(type){
      case A:
        return A.fromJson(data);
        case A?: // Getting error Conditions must have a static type of 'bool'
          return A.fromJson(data);
      case B:
        return B.fromJson(data);
    }
  }

Answer 1

You can create a function Type getType<T>() => T;, but since getType<A?>() would not be considered a constant value, you would not be able to use it with a switch statement:

Type getType<T>() => T;

dynamic dataFactory(Type type, Map<String, dynamic> data) {
  if (type == A || type == getType<A?>()) {
     return A.fromJson(data);
  } else if (type == B) {
     return B.fromJson(data);
  }
  ...
}

Another approach would be to use a Map of callbacks:

Type getType<T>() => T;

final _factoryMap = <Type, dynamic Function(Map<String, dynamic>)>{
  A: A.fromJson,
  getType<A?>(): A.fromJson,
  B: B.fromJson,
};

dynamic dataFactory(Type type, Map<String, dynamic> data) =>
    _factoryMap[type]?.call(data);