Deleting from an array of objects

[Chris Holbrook]

Apparently once you have made and array of objects, you cannot delete a member using ARRAY DELETE.

This workaround seems to work, but I would appreciate any observations....

'--------------------------------------------------------------------------------
' delete the lx'th object from the global array gBX and shuffle the array down, redim to remove topmost member
sub DeleteObject (lx as long)
    local i, n as long

    n = ubound(gBX)
    gBX(lx) = nothing
    for i = lx to n -1
        gBX(i) = gBX(i + 1)
    next
    gBX(n) = nothing
    if n > 0 then
        redim preserve gBX(0 to n-1) as global ICtlBox
    else
        erase gBX()
    end if
end sub

[Mark Smit]

Hey Chris,

This is what I do...

dim lMinRow as long
dim lMaxRow as long

lMinRow = lbound(m_Objects)
lMaxRow = ubound(m_Objects)

m_Objects(lRow) = nothing

redim Index(lMinRow to lMaxRow) as dword at varptr(m_Objects(lMinRow))
array delete Index(lRow)

[Chris Holbrook]

Mark, that looks like an index, so the array of interfaces never changes? That would work OK unless you had a great turnover of objects. In fact it would be quite efficient. Thanks!

BTW I have it on good authority that none of the the ARRAY statements work with interface arrays.

[Mark Smit]

Hey Chris,

Well it's not actually an Index per say...

The array of objects, "under the hood" is nothing more than an array of DWORDs. So if you allocate an array of DWORDs over top (DIM AT) then you can use ARRAY DELETE to remove that element via the overlapped array.

Maybe one of the Guru's can confirm this idea so we can both feel better about using it

[Steve Rossell]

The array of objects, "under the hood" is nothing more than an array of DWORDs. So if you allocate an array of DWORDs over top (DIM AT) then you can use ARRAY DELETE to remove that element via the overlapped array

That will work but this will not reduce the reference count. I would do a arrayofobjs(i)=NOTHING before I did an array delete on it.

[Mark Smit]

Yup, that was in the example I posted

m_Objects(lRow) = nothing

[Michael Mattias]

BTW I have it on good authority that none of the the ARRAY statements work with interface arrays

If that's a design restriction it should be in the help file under ARRAY DELETE.

It ain't.

[Chris Holbrook]

It ain't.

yet.

[Michael Mattias]

That must be a "confirmed" bug. (Yes, a "bug" can be present in the help file)

I will no longer be referring to "known" bugs, as none have been placed in the PowerBASE forum and therefore are not known to anyone who could actually use that information to avoid spending ANOTHER hour and half (two such sessions already) trying to make something which never had a chance of working work.

Neither the five bugs I have personally found and reported and have been "confirmed" by PB support, nor the twenty more neatly itemized in the 'history.txt' file included with the first 9.0.1 beta release which was sent to me unsolicited should be considered "known."

MCM

[colin glenn]

I am so glad to have found this out before finding this out.

[Michael Mattias]

The bummer is, you just don't know:

Is ARRAY DELETE *not* supported for an array of objects, in which case there are errors in both the help file and the compiler (if not supported, should generate a compile-time error)?

Or,

Is ARRAY DELETE *supposed* to work with arrays of objects, in which case the bug is ONLY in the compiler?

Enquiring minds....yadda yadda...

[Bob Zale]

Your remarks are not simply disingenuous, they are dead wrong. I hope everyone will disregard this remark from Mr. Mattias as it's false and misleading.

Best regards,

Bob Zale
PowerBASIC Inc.

[Michael Mattias]

A disingenuous question? That's a new one on me.

Given Mr. Holbrook's code - which I have not tried myself, but I trust him - demonstrates that ARRAY DELETE does not delete elements from an array of objects, which is it?

Does the help file fail to state and the compiler fail to detect an unsupported use of ARRAY DELETE, or does the compiler simply not generate the correct code to effect an ARRAY DELETE when called?

If it's not supported, fine. Just say so.

If it's a code-generation error, fine. Just say so.

The point is, we - your customers - have no way to know.

MCM

[Bob Zale]

What happened when you tried it?

(Where have I heard that phrase before?)

It's not nice, nor is it productive, to mislead our friends here, so please try to restrain yourself. You comments are dead wrong, so please try to keep them contained?

[Michael Mattias]

>What happened when you tried it?

What happened was, valid ARRAY DELETE syntax was rejected by the compiler, that's what happened.

'tarraydelo.bas

#COMPILE EXE
#DIM ALL
#INCLUDE "WIN32API.INC"
#INCLUDE   "VBAPI32.INC"       'required as of 11/28/08 (safeArray functions)
#INCLUDE   "ADODB28DISP.INC"  ' regenerated with CC5 com browser "dispatch only"

GLOBAL gbx() AS Int__Connection

FUNCTION PBMAIN () AS LONG
    
 LOCAL I AS LONG, bGoodObjects AS LONG
    
 REDIM  gbx (9)
 
 FOR i = 0 TO 9
     LET  gbx(I) = NEWCOM $PROGID_ADODB_Connection
     IF OBJRESULT <>%S_OK THEN
           MSGBOX "Object Creation Failed"
           EXIT FUNCTION
     END IF
 NEXT
 
 ' test that our objects are good
 
 GOSUB TestForGoodobjects
 
 ' let's try to delete an element using valid ARRAY DELETE syntax:
 ARRAY DELETE gbx(5)   ' compiler error: Error 482 datatype mismatch
 
 GOSUB TestForGoodObjects
 
 
 EXIT FUNCTION
  
 
TestForGoodObjects:
  bGoodObjects = %TRUE
  FOR I = LBOUND (gbx,1) TO UBOUND (gbx,1)
      IF ISFALSE ISOBJECT (gbx(i))  THEN
          MSGBOX USING$ ("Bad object at subscript #", i)
          bGoodObjects = %FALSE
          EXIT FOR
      END IF
  NEXT
  
  RETURN
          
      
END FUNCTION

PowerBASIC for Windows
PB/Win  Version 9.00 
Copyright (c) 1996-2008 PowerBasic Inc.
Venice, Florida USA
All Rights Reserved

Error 482 in D:\SOFTWA~1\pbwin80\work\testarraydeleteobject.bas(34:015):  Data type mismatch
Line 34:  ARRAY DELETE gbx(5)   ' compiler error: Error 482 datatype mismatch

(reported to PB support)

[Bob Zale]

Please stop misleading the folks. It isn't nice.

[Mark Smit]

Hey Bob,

Am I missing something?

Michael's code example produces the same results on my end? Are you saying that ARRAY DELETE is supposed to work on arrays of objects?

Thanks

[Michael Mattias]

At least one of us is now thoroughly confused.

I'll wait to see what PB Support says.

Oops, I did not send the included file ADODBDISP28.INC, generated by the COM browser. I better resend that. I used the factory-supplied WIN32API.INC and VBAPI.INC files.

[Bob Zale]

No, Mark, PowerBASIC generates a very polite exception report of a DATA TYPE MISMATCH if you try to use any ARRAY statement with an array of objects. Can you just imagine trying to SORT or SCAN an array of objects when the various forms are so deeply intertwined?

Mr. Mattias falsely claimed that no compile-time exception was generated:

"Does the...compiler fail to detect an unsupported use of ARRAY DELETE"
No
"...or does the compiler simply not generate the correct code to effect an ARRAY DELETE when called?"
No

Best regards,
Bob

[Chris Holbrook]

oops!