Pattern 5: Custom Functions

Define in adapter-registration.yaml

custom_functions:
  ElevatorControl:
    description: "Elevator floor access control"
    states:
      - pq.state.elevator.idle
      - pq.state.elevator.moving
      - pq.state.elevator.fault
    properties:
      current_floor:
        type: int
        default: 1
      target_floor:
        type: int
        default: 1
    actions:
      FloorRequested:
        description: "User requested floor access"
        target_state: "pq.state.elevator.moving"
        events:
          - pq.event.elevator.floor.requested
      FloorReached:
        description: "Elevator arrived at floor"
        target_state: "pq.state.elevator.idle"
        events:
          - pq.event.elevator.floor.reached
      Fault:
        description: "Elevator malfunction"
        target_state: "pq.state.elevator.fault"
        events:
          - pq.event.elevator.fault

Generated Interface

// .GeneratedFiles/.../IElevatorControlFunction.g.cs
public interface IElevatorControlFunction : IFunction
{
    int CurrentFloor { get; }
    int TargetFloor { get; }
    Task SetIdle(CancellationToken cancellationToken);
    Task SetMoving(CancellationToken cancellationToken);
    Task SetFault(CancellationToken cancellationToken);
}

Usage

// In ElevatorDevice.cs
internal sealed partial class ElevatorDevice
{
    internal async Task OnFloorRequested(uint floor)
    {
        ElevatorControl.CurrentFloor = (int)floor;
        await ElevatorControl.SetMoving(CancellationToken.None);
    }

    internal async Task OnFloorReached(uint floor)
    {
        ElevatorControl.TargetFloor = (int)floor;
        await ElevatorControl.SetIdle(CancellationToken.None);
    }
}

When to Use Custom Functions

Use custom functions for device-specific capabilities not covered by standard functions:

• Special access modes (elevator floors, parking levels)
• Device-specific states (patrol mode, test mode)
• Proprietary features unique to vendor

Standard functions (Door, Reader, Power, etc.) should be used whenever possible.