Hello,

I have a FB with 2 REFERENCE TO FB as input parameters.
In the FB, i want to work with either the first or the second Reference depending on a variable (NumSupport)
But when I try to affect the RefSupport:=RefSupport1, I get an exception.
Does anyone know how to deal with this problem ? What is correct way to work ?

Thank you

FUNCTION_BLOCK FB_Manip
VAR_INPUT
RefSupport1 : REFERENCE TO FB_Support;
RefSupport2 : REFERENCE TO FB_Support;
END_VAR
VAR
RefSupport : REFERENCE TO FB_Support;
NumSupport: INT:=1;
END_VAR

IF NumSupport=1 THEN
RefSupport:=RefSupport1;
ELSE
RefSupport:=RefSupport2;
END_IF

The operator generates a reference (pointer) to a value;

   RefSupport REF= RefSupport1;

see https://help.codesys.com/webapp/_cds_ref_assignment;product=codesys;version=3.5.17.0

TIP: use a CASE statement for NumSupport instead of a IF THEN, that way you can easily extend your code in the future i.e;

CASE NumSupport OF

    1: ;

    2: ;

ELSE
    ;

END_case;

You could also use VAR_IN_OUT and not do VAR_INPUT and then declare a reference

https://help.codesys.com/webapp/_cds_vartypes_var_in_out;product=codesys;version=3.5.17.0

Best regards,
Marcel