Release SP20 - Changes in behaviour?

2024-03-25T17:58:55.148000Z

This... is not very practical for me - as I have a bunch of different classes - it's just doesn't seems to be very practical to define a NULL for each of them...

Something like this I use in parameter definitions. For example:

VAR_INPUT
    refVFD_Drive : REFERENCE TO FB_VFD_Drive := GVL_DUMMY.Dummy_VFD;
END_VAR

I use this to prepare objects for code I don't control: Typycally visualizations - had many troubles with references set on the fly, right before opening a corresponding visualization...

And yes, the instance in GVL_Dummy reports itself as "Fake", so it does not influence the actual application at all. Actually this way I could invalidate a reference, just to set it to a "Dummy" instance.

Release SP20 - Changes in behaviour?

2024-03-25T17:49:36.403000Z

Wow.... I missed this one in the manual - so there is a special syntax to invalidate a reference... Great :) Seems to work.
(it's just mentionned in the examples line)...

I've always assigned 0 to the variable, with := 0 - like setting a pointer to 0. In theory, that should work as well.

Thanks!

Release SP20 - Changes in behaviour?

2024-03-25T17:49:29.181000Z

Wow.... I missed this one in the manual - so there is a special syntax to invalidate a reference... Great :) Seems to work.
(it's just mentionned in the examples line)...

I've always assigned 0 to the variable, with := 0 - like setting a pointer to 0. In theory, that should work as well.

Thanks!

Release SP20 - Changes in behaviour?

2024-03-25T02:49:28.690000Z

You should use this method:
VAR
NULL:REFERENCE TO FB_MSG
END_VAR
Add_EVT_OUT REF= NULL;

Release SP20 - Changes in behaviour?

2024-03-24T19:06:48.159000Z

use this to set an invalid reference

Add_EVT_OUT REF= 0;

Release SP20 - Changes in behaviour?

2024-03-24T08:55:47.943000Z

Dear all,

I've just started to migrate some of my ancient projects to SP20. There is one strange error (?) I have noticed so far. In a method call, depending on the circumstances I would like to return reference to an object, or an invalid reference:

METHOD Add_EVT_OUT : REFERENCE TO FB_MSG
VAR
END_VAR

IF __ISVALIDREF(refMSG_Entry) THEN
    Add_EVT_OUT REF= MANAGER.AddMsg_EVT_OUT(
        refMSG_Entry, 
        _Get_EVT_Message(MSG_EVENT.OUT), 
        _Get_EVT_AddCode(MSG_EVENT.OUT)
    )^;
ELSE
    Add_EVT_OUT := 0;
END_IF

So far setting a reference variable to 0, did this. But now, the expression Add_EVT_OUT := 0; gives an error:

[ERROR] DB_WTP_370: Add_EVT_ACK MSG_TRIGGER_EXT: C0032: Cannot convert type 'BIT' to type 'REFERENCE TO FB_MSG'

Naturally... I can write:

    Add_EVT_OUT := DWORD#0;

But is this the correct way? Is there any constant I could use instead, like "NULL"?
Or this is totally wrong and to be avoided?

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