JSON serialization

This is how a protocol in Dart becomes the protocol.json the app and the Portal read. See the generated example in Configure your study.

Where in the repo

File	What is in it
`carp_mobile_sensing.json.dart`	Registers every CAMS class for deserialization
`domain.g.dart`, `runtime.g.dart`	Generated by `json_serializable`

How it works

Extension to CAMS often rely on serialization to/from JSON - this applies for triggers, measures, sampling schemas, data, etc. CAMS relies on polymorphic serialization as supported by the carp_serializable package, which is an extension to the standard json_serializable provided in Dart.

Support for polymorphic JSON serialization implies four steps when designing your classes:

Define a serializable class

Extend from Serializable and annotate the class:

@JsonSerializable(includeIfNull: false, explicitToJson: true)
class FreeMemory extends Data {
  ...
}

JSON serializable methods

Implement the three JSON serializable methods:

  @override
  Function get fromJsonFunction => _$FreeMemoryFromJson;
  factory FreeMemory.fromJson(Map<String, dynamic> json) =>
      FromJsonFactory().fromJson<FreeMemory>(json);
  @override
  Map<String, dynamic> toJson() => _$FreeMemoryToJson(this);

Registration
Register the class’s fromJsonFunction in the FromJsonFactory, e.g. in the onRegister() callback function of a sampling package:
```
  @override
  void onRegister() {
    FromJsonFactory()
        .register(FreeMemory()));
  }
```
Running the code generator
When all JSON classes have been implemented, the final step is to generate the JSON serialization helper classes. These can be generated using build_runner, by running the following command in the root of your Flutter project:
Terminal window
```
dart run build_runner build --delete-conflicting-outputs
```
This will generate the necessary .g.dart files.