Presenter Contract¶

`presenter_contract` ¶

Contract for presentation adapters in a hexagonal architecture.

Presentation adapters format data for external consumers (CLI, web, API, etc.).
They define how application responses are rendered, keeping formatting logic
out of the application layer.

`PresenterPort` ¶

Bases: InboundPort

Contract for presentation adapters.

Responsibilities

Define the contract for formatting application responses.
Keep presentation logic outside the application core.
Support multiple output formats (CLI, API, UI).

Non-Responsibilities

Implement business logic.
Handle infrastructure concerns (HTTP, I/O) — those are adapters.

Example

import sys


class CliPresenter(PresenterPort[str]):
    async def present(self, response: str) -> None:
        print(f"Result: {response}")

    async def present_error(self, error: Exception) -> None:
        print(f"Error: {error}", file=sys.stderr)

Source code in src/forging_blocks/presentation/presenter_contract.py

class PresenterPort[ResponseType](InboundPort):
    """Contract for presentation adapters.

    Responsibilities:
        - Define the contract for formatting application responses.
        - Keep presentation logic outside the application core.
        - Support multiple output formats (CLI, API, UI).

    Non-Responsibilities:
        - Implement business logic.
        - Handle infrastructure concerns (HTTP, I/O) — those are adapters.

    Example:
        ```python
        import sys


        class CliPresenter(PresenterPort[str]):
            async def present(self, response: str) -> None:
                print(f"Result: {response}")

            async def present_error(self, error: Exception) -> None:
                print(f"Error: {error}", file=sys.stderr)
        ```
    """

    @abstractmethod
    async def present(self, response: ResponseType) -> None:
        """Render the application response to the output channel.

        Args:
            response: Domain/output data produced by the application.

        Notes:
            - Output channel (terminal, API, file) is adapter-specific.
            - Must not modify the response data.

        """
        ...

    @abstractmethod
    async def present_error(self, error: Exception) -> None:
        """Render an error to the output channel.

        Args:
            error: Exception from the application layer.

        Notes:
            - Must preserve error context for diagnostics.
            - Output format is adapter-specific.

        """
        ...

`present(response: ResponseType) -> None` `abstractmethod` `async` ¶

Render the application response to the output channel.

Parameters:

Name	Type	Description	Default
`response`	`ResponseType`	Domain/output data produced by the application.	required

Notes

Output channel (terminal, API, file) is adapter-specific.
Must not modify the response data.

Source code in src/forging_blocks/presentation/presenter_contract.py

@abstractmethod
async def present(self, response: ResponseType) -> None:
    """Render the application response to the output channel.

    Args:
        response: Domain/output data produced by the application.

    Notes:
        - Output channel (terminal, API, file) is adapter-specific.
        - Must not modify the response data.

    """
    ...

`present_error(error: Exception) -> None` `abstractmethod` `async` ¶

Render an error to the output channel.

Parameters:

Name	Type	Description	Default
`error`	`Exception`	Exception from the application layer.	required

Notes

Must preserve error context for diagnostics.
Output format is adapter-specific.

Source code in src/forging_blocks/presentation/presenter_contract.py

@abstractmethod
async def present_error(self, error: Exception) -> None:
    """Render an error to the output channel.

    Args:
        error: Exception from the application layer.

    Notes:
        - Must preserve error context for diagnostics.
        - Output format is adapter-specific.

    """
    ...

Presenter Contract¶