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Query

query

Module defining the base Query class for queries.

Query

Bases: Message[QueryPayloadType]

Base class for all queries.

Queries represent a request to retrieve data from the system.
They are handled by query handlers and should not modify state.

Queries are named in interrogative mood (e.g., GetOrder, FindCustomer,
ListProducts).

Example 
class GetOrderPayload:
    def __init__(self, order_id: str) -> None:
        self.order_id = order_id


class GetOrder(Query[GetOrderPayload]):
    def __init__(self, order_id: str):
        super().__init__()
        self._order_id = order_id

    @property
    def _payload(self) -> GetOrderPayload:
        return GetOrderPayload(order_id=self._order_id)

    @classmethod
    def from_payload_fields(
        cls, data: GetOrderPayload, metadata: MessageMetadata
    ) -> "GetOrder":
        return cls(order_id=data.order_id)

    @property
    def value(self) -> GetOrderPayload:
        return self._payload
Source code in src/forging_blocks/domain/messages/query.py 
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class Query[QueryPayloadType](Message[QueryPayloadType]):
    """Base class for all queries.

    Queries represent a request to retrieve data from the system.
    They are handled by query handlers and should not modify state.

    Queries are named in interrogative mood (e.g., GetOrder, FindCustomer,
    ListProducts).

    Example:
        ```python
        class GetOrderPayload:
            def __init__(self, order_id: str) -> None:
                self.order_id = order_id


        class GetOrder(Query[GetOrderPayload]):
            def __init__(self, order_id: str):
                super().__init__()
                self._order_id = order_id

            @property
            def _payload(self) -> GetOrderPayload:
                return GetOrderPayload(order_id=self._order_id)

            @classmethod
            def from_payload_fields(
                cls, data: GetOrderPayload, metadata: MessageMetadata
            ) -> "GetOrder":
                return cls(order_id=data.order_id)

            @property
            def value(self) -> GetOrderPayload:
                return self._payload
        ```

    """

    @property
    @abstractmethod
    def _payload(self) -> QueryPayloadType:
        """Return the query-specific payload data.

        Subclasses MUST implement this property to return the query-specific
        data.
        """