Loading data into Globals

[Bud Durland]

There's a very good chance I'm over thinking this, but here it is. I'm moving a segment of code that loads data records from the database into a data structure into it's own include file. Splitting it out because I now have more than one program that needs to so work with this data. The program that originally used this logic put the data into global variables. The new programs will not; the data will be local to the function using it.

Here's the over-thinking part: it just feels like I should not be passing the global variables as parameters to the load function. Sample code below, not the most beautiful code, but I think it shows my point. For some reason, option 2 seems more correct, but I can't really say why. Hoping to benefit from others experience.

#COMPILE EXE
#DIM ALL

#INCLUDE "windows.inc"

TYPE MyheaderType
  Element1 AS LONG
  element2 AS LONG
END TYPE

TYPE MyDetailtype
  idx     AS LONG
  Squared AS QUAD
END TYPE

GLOBAL  gHeaderData          AS MyHeaderType
GLOBAL  gDetailData()        AS MyDetailType
GLOBAL gCS                   AS Critical_Section

FUNCTION PBMAIN () AS LONG

  LOCAL Success           AS LONG
  LOCAL xLoop             AS LONG
  
  LOCAL lHeaderData       AS MyHeaderType
  LOCAL lDetailData()     AS MyDetailType

  REDIM lDetailData(0 TO 0)
  REDIM gDetailData(0 TO 0)

  ' Option 1
  Success = LoadData(gheaderData, gDetailData())
  IF ISTRUE(Success) THEN
    ? "loaded!"
  ELSE
    ? "Epic failure!"
  END IF

  ' option 2
  Success = LoadData(lHeaderData, lDetailData())
  IF ISTRUE(Success) THEN
    EnterCriticalSection gCS
    gHeaderData = lHeaderData
    REDIM gDetailData(1 TO UBOUND(lDetailData))
    FOR xLoop = 1 TO UBOUND(lDetailData)
      gDetailData(xLoop) = lDetailData(xLoop)
    NEXT xLoop
    LeaveCriticalSection gCS
    ? "loaded!"
  ELSE
    ? "Epic failure!"
  END IF


END FUNCTION

FUNCTION LoadData(DataHeader AS MyheaderType, DataDetail() AS myDetailType) AS LONG

  LOCAL xLoop      AS LONG

' get header data
  DataHeader.Element1 = 1
  DataHeader.Element2 = 2

' Load details
  REDIM DataDetail(1 TO 10)
  FOR xLoop = 1 TO 10
    DataDetail(xLoop).idx = xLoop
    DataDetail(xLoop).Squared = (xLoop ^ 2)
  NEXT xLoop

  FUNCTION = 1

END FUNCTION​

[Michael Mattias]

1. To pass values, If you are not going to alter the variable, you may use the BYVAL or BYCOPY options.

2. Why load up the header and ALL the lines? You can do each line as needed by putting in a FETCH loop.

3. Number of lines = SELECT COUNT (*) FROM tablename WHERE orderNumber = Header.OrderNumber. You can then presize any PB array needed which will be much more efficient than REDIM PRESERVE for each line or even every "n" lines. Not the case here, but a reminder for lurkers,

[Michael Mattias]

Here's the over-thinking part: it just feels like I should not be passing the global variables as parameters to the load functio

No reason not to. But if you are going to pass it, why make it GLOBAL? Just define/declare it in some procedure and pass it as a param to all procedures further down the call chain. That's what I do.

[Bud Durland]

1. To pass values, If you are not going to alter the variable, you may use the BYVAL or BYCOPY options.

I realize that, but I need the data back to the caller. I'm sorry, I thought I mentioned that the purpose of the function is fetch data from the database and load it into variables.

2. Why load up the header and ALL the lines? You can do each line as needed by putting in a FETCH loop.

Because I need them all in memory at once to perform certain data manipulations

3. Number of lines = SELECT COUNT (*) FROM tablename WHERE orderNumber = Header.OrderNumber. You can then presize any PB array needed which will be much more efficient than REDIM PRESERVE for each line or even every "n" lines. Not the case here, but a reminder for lurkers,

Exactly what I'm doing in the real code (well, close enough, thanks to Eric Pearson and SQL_ResultRowCount() in SQL Tools) but I didn't think it was relevant to the core question of whether there is some subtle issue with passing the globals directly to the function. Depending on the program that is using this function, the variables used by the program may be globals, or they may be local to the calling procedure. Should I, when the program is using globals, use Option 2 to load the data, or is just passing the global var BYREF ok?

[Stuart McLachlan]

. Should I, when the program is using globals, use Option 2 to load the data, or is just passing the global var BYREF ok?

Perfectly OK to pass the global array BYREF. To do otherwise is just additonal work for no benefit.
If you want to fill a global array, pass it - if you want to fill an array that is local to the calling function, just pass that.

[Bud Durland]

Perfectly OK to pass the global array BYREF.

That's the question I had. Thanks for the input.