Hooks

Field Hooks

Field hooks enable fine-grained control over the serialization of individual fields. They are implemented by mixing in the FieldSerializationHook interface on a class that also implements StructureMetadata.

Field hooks are executed for structure converters when using the NativeSerializerMode. They receive the field context and are able to modify the serialized map after a field has been serialized as well as before it is deserialized.

Field Serialization Hook Example

class MultiplyByTwo extends StructureMetadata with FieldSerializationHook {
  const MultiplyByTwo();

  @override
  void postFieldSerialization(
      NativeStructureContext context,
      NativeStructureFieldContext fieldContext,
      Map<String, dynamic> map,
      DogEngine engine) {
    final value = map[fieldContext.key] as int?;
    if (value != null) map[fieldContext.key] = value * 2;
  }

  @override
  void beforeFieldDeserialization(
      NativeStructureContext context,
      NativeStructureFieldContext fieldContext,
      Map<String, dynamic> map,
      DogEngine engine) {
    final value = map[fieldContext.key] as int?;
    if (value != null) map[fieldContext.key] = value ~/ 2;
  }
}

The hook can then be applied to a field like any other annotation:

@serializable
class Example with Dataclass<Example> {

  @MultiplyByTwo()
  int number;

  Example(this.number);
}

Structure Hooks

Structure hooks operate on the entire serialized map of a class. They are implemented by extending the SerializationHook class or implementing it. You can apply them to a structure by annotating the class with the annotation that extends SerializationHook.

Structure hooks are executed for structure converters when using the NativeSerializerMode. They receive the full structure map and can freely modify it before deserialization or after serialization.

Structure Serialization Hook Example

class ExampleHook extends SerializationHook {
  const ExampleHook();

  @override
  void beforeDeserialization(
      Map<String, dynamic> map,
      DogStructure structure,
      DogEngine engine) {
    map['decoded_at'] ??= DateTime.now().toIso8601String();
  }

  @override
  void postSerialization(
      dynamic obj,
      Map<String, dynamic> map,
      DogStructure structure,
      DogEngine engine) {
    map['encoded_at'] ??= DateTime.now().toIso8601String();
  }
}