Dynamic variables

mapp Services V5.16

Navigation over dynamic data is supported using dereference operator "^". This operator is used to continue a variable reference through levels of "REFERENCE TO" data types if automatic dereferencing is not enabled.

Reference variables are automatically dereferenced.

Structure members are not dereferenced.

Example

TYPE
  Tool : STRUCT
    id : DINT;
    radius : LREAL;
  END_STRUCT;
  ToolSet : STRUCT
    main : Tool;
    alt : REFERENCE TO Tool;
  END_STRUCT;
END_TYPE
VAR
  Ts : ToolSet;
  Tptr : REFERENCE TO ToolSet;
END_VAR
PROGRAM _MAIN
  (* Configure REFERENCE TO addresses *)
  Tptr ACCESS ADR(Ts);  (* Use ACCESS for auto-dereferenced variable *)
  Tptr.alt := ADR(Tptr.main);
  (* Access through REFERENCE TO data members *)
  Tptr.alt^.id := 1;
END_PROGRAM

Navigation	Data type	Notes
Tptr	ToolSet	Automatically dereferenced (points to Ts)
Tptr.main	Tool
Tptr.alt	REFERENCE TO tool	Pointer to tool (in Ts.main)
Tptr.alt^	Tool	Tool data from Ts.main
Tptr.main.id	DINT
Tptr.alt^.id	DINT	Navigates across the reference