Dynamic List in Flutter for Json - json

Question

I'm working with some complex json in dart, and I have an issue creating objects before I know what type they'll be.
I appreciate the suggestions, but I don't think I completely understand. In the given answer:
var entity = Model();
castToEntity(entity, {'test': 10});
Don't I need to know that it will be a Model class?
What if I have the below two classes:
#JsonSerializable(explicitToJson: true, includeIfNull: false)
class Location {
String id;
String resourceType;
Location({#required this.id, this.resourceType})
factory Location.fromJson(Map<String, dynamic> json) => _$LocationFromJson(json);
Map<String, dynamic> toJson() => _$LocationToJson(this);
}
class Reference {
String reference;
String resourceType;
Location({#required this.reference, this.resourceType}
factory Reference.fromJson(Map<String, dynamic> json) => _$ReferenceFromJson(json);
Map<String, dynamic> toJson() => _$ReferenceToJson(this);
}
And then I query the server, and I don't know what kind of class it will be. It could be a Location, or a Reference, or if it's a list, it could be multiple of both, and I don't know until I've requested it.
var myBundle = Bundle.fromJson(json.decode(response.body));
Each "myBundle.entry" is another resource. I'd like to be able to use information from that resource to define itself. So I could do something like:
myBundle.entry.resourceType newResource = new myBundle.entry.resourceType();
What I'm doing right now is sending it to a function that has all of the possible options predefined:
var newResource = ResourceTypes(myBundle.entry[i].resource.resourceType,
myBundle.entry[i].resource.toJson());
dynamic ResourceTypes(String resourceType, Map<String, dynamic> json) {
if (resourceType == 'Location') return (new Location.fromJson(json));
if (resourceType == 'Reference') return (new Reference.fromJson(json));
}
It was said that there's not reflection in dart, so I didn't know any other way to do it.

Answer 1

As far as I know, it's not possible since Dart doesn't have Reflection like c#, the most close that I can imagine, is using an abstract class that enforces your entity to implement fromJson, and, in that method, you read the Map and put values into fields, like the code below:
abstract class Serializable {
void fromJson(Map<String,dynamic> data);
}
class Model implements Serializable {
int test;
#override
void fromJson(data) {
test = data['test'];
}
}
Serializable castToEntity(Serializable entity, Map<String, dynamic> data) {
return entity..fromJson(data);
}
Now, when you read you database and have the Map, you can call a method generic like:
var entity = Model();
castToEntity(entity, {'test': 10});
print(entity.test);
Where entity is an empty model.
Note: Your fields on entity, cannot be final, since fromJson is an instance method and not a factory method.