I'm using Wago PFC200 for my home automation. I got base function block:

FUNCTION_BLOCK ABSTRACT Room

and two the interface:

INTERFACE IBlinds
- BlindsUp
- BlindsDown 

and

ILights
-TurnOffLights
-TurnOnLights

My room's instances looks like this:

FUNCTION_BLOCK Garage EXTENDS Room IMPLEMENTS ILights, IBlinds

In my PLC_PRG I've all instances of my rooms:

PROGRAM PLC_PRG
VAR
    Bedroom: Bedroom;
    Garage: Garage; 
    Hall: Hall;
    Boilerroom: Boilerroom;
    ...
END_VAR

Under the PLC_PRG I've some methods to e.g.: automate blinds:

METHOD MoveBlindsToMorningPosition
VAR CONSTANT
    siCount: SINT := 5;
END_VAR
VAR_INPUT
    xMoveSignal: BOOL;
END_VAR
VAR
    _siIndex: SINT;
    _rooms: ARRAY[0..siCount] OF POINTER TO IBlinds := [ADR(Livingroom), ADR(Diningroom), ADR(Kitchen), ADR(Toilet), ADR(Boilerroom), ADR(Garage)];
END_VAR

FOR _siIndex := 0 TO siCount DO
    _rooms[_siIndex]^.MoveBlindsToMorningPosition(xMove := xMoveSignal);
END_FOR

But I got following compilation errors for each room in the _rooms array: C0032: Cannot convert type 'POINTER TO Garage' to type 'POINTER TO IBlinds'

My function block implements IBlinds. Is there a way to cast function block?

Hey,
I think you are looking for QUERYINTERFACE https://help.codesys.com/webapp/_cds_operator_queryinterface;product=codesys;version=3.5.16.0
Dont forget to add EXTENDS __System.IQueryInterface to your interfaces

Best regards,
Marcel

Try removing "POINTER TO" in the declaration of _rooms. It does seem intuitive to need the Pointer To, but the language takes care of the managing the pointer for you. The pointer is implied.

@GaryPratt I learned that yesterday evening by reading the CodeSys documentation where it is stated that:

CODESYS always treats variables declared with the type of an interface as references