RField

Resource field with custom serialization/deserialization support.

RField extends BaseRField to provide custom serialization and deserialization logic. This is useful when the field value needs special handling for storage (e.g., complex objects, encrypted data, compressed content).

The field is automatically persisted when a Resource is output from a task and automatically restored when the Resource is loaded as input to another task.

Custom serialization can be implemented in two ways:

Pass serializer/deserializer functions to init
Subclass RField and override the serialize/deserialize methods

Attributes: _deserializer: Optional function to convert stored values to runtime values _serializer: Optional function to convert runtime values to storable values

Example: ```python import json

class MyResource(Resource):
    # Using serializer/deserializer functions
    metadata = RField(
        serializer=lambda x: json.dumps(x),
        deserializer=lambda x: json.loads(x),
        default_value=dict,
        storage=RFieldStorage.KV_STORE
    )

    # Simple field with no custom serialization
    description = RField(storage=RFieldStorage.KV_STORE)
```

```python
# Alternative: Subclass approach
class JsonRField(RField):
    def serialize(self, value):
        return json.dumps(value) if value is not None else None

    def deserialize(self, value):
        return json.loads(value) if value is not None else None
```

Attributes

include_in_dict_view: boolstorage: RFieldStorage

Functions

__init__

Initialize an RField with optional custom serialization logic.

deserializer : collections.abc.Callable[[typing.Any], typing.Any] | None

Function to deserialize stored values (storage -> runtime). Signature: (stored_value: Any) -> runtime_value: Any If None, no custom deserialization is performed. Defaults to None

serializer : collections.abc.Callable[[typing.Any], typing.Any] | None

Function to serialize runtime values (runtime -> storage). Signature: (runtime_value: Any) -> stored_value: Any If None, no custom serialization is performed. Defaults to None

Default value for the field. Can be a primitive, Type, or Callable. See BaseRField.__init__ for details. Defaults to None

include_in_dict_view : bool - False

Whether to include this field in dict/JSON views. Use False for large or sensitive data. Defaults to False

storage : RFieldStorage - RFieldStorage.KV_STORE

Storage backend for persistence (DATABASE, KV_STORE, or NONE). Defaults to KV_STORE for efficient storage of larger values

deserialize

Deserialize a stored value into the field's runtime representation.

This method is called when loading a field value from storage. If a custom deserializer function was provided during initialization, it will be used. Otherwise, the value is returned as-is.

Can be overridden in subclasses to implement class-level deserialization logic.

r_field_value : Any

The raw value retrieved from storage

Return type : Any

get_default_value

Get the default value for this field.

If the default value is a Type or Callable, it will be called to generate a new default value. Otherwise, the default value is returned directly.

This ensures that mutable defaults (like lists or dicts) are not shared between Resource instances.

Return type : Any

serialize

Serialize the field's runtime value into a storable representation.

This method is called when saving a field value to storage. If a custom serializer function was provided during initialization, it will be used. Otherwise, the value is returned as-is.

Can be overridden in subclasses to implement class-level serialization logic.

r_field_value : Any

The current runtime value in the Resource

Return type : Any

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