Globals vs Local and passing pointers

[Cliff Nichols]

One of the few things I do not do often (knowingly at least) is manipulate pointers. So I have to ask if I have a fatal flaw with a thought I had.

If I do not use a Global, but instead a function to Set or Get a value and then locally have that value, would the following be valid?

FUNCTION SetGetLogErrors(ValueToSet AS LONG, ValueResults AS LONG, ResetValue AS LONG) AS LONG
          STATIC FunctionValue AS LONG                                                    'Static to hold current value
          SELECT CASE ResetValue                                                          'Decide whether to Set or to Get the current value
               CASE %False, %UNKNOWN_VALUE                                                'If set to False, or -1 Then Get Current Value
                    ValueResults = FunctionValue                                          'Return Results as a parameter
               CASE = %TRUE                                                               'If set to True then Reset the Current Value
                    FunctionValue = ValueToSet                                            'Reset the value
                    ValueResults = FunctionValue                                          'Return Results as a parameter
          END SELECT
          FUNCTION = %False                                                               'Return if Function Failed
     END FUNCTION

If I change something in the value passed, do I need to change the pointer? aka update ValueToSet to VarPtr(Variable), or am I just "Lucking Out" that I have not run into a problem yet?

[Michael Mattias]

As long as the variable in the procedure is STATIC or GLOBAL, you don't even need to pass the value to be set as a parameter, you can return it directly as the function's return value if convenient. (Although I, like your example, prefer to pass these values so I can use the return value as a "success/fail" indicator).

'STATIC somevalue' in a procedure dedicated to "getting or setting" is a perfectly safe and valid way to maintain a global (small G) value... it's just that you will need a procedure call to get it when you need it instead of just using the name of a GLOBAL variable.

If you were looking for something a tad geekier... the address of STATIC and GLOBAL variables does not change during a process; it remains the same from the time the module in which that variable is defined as STATIC or GLOBAL is loaded until it is unloaded.


MCM

[Scott Turchin]

If you do a search here - Michael showed me a great way to pass pointers using the callback CALL - so you won't need ANY globals - albeit I still used a few..

Works great -

[Mike Doty]

Since this is probably just logic these notes may not apply:

1. Logic seems correct
2. %UNKNOWN_VALUE used a CASE ELSE instead for %FALSE and unknown
3. FUNCTION always returns %FALSE

 
FUNCTION SetGetLogErrors(ValueToSet AS LONG, ValueResults AS LONG, ResetValue AS LONG) AS LONG
  STATIC FunctionValue AS LONG                'Static to hold current value
  SELECT CASE ResetValue                      'Decide whether to Set or to Get the current value
 
    CASE %TRUE                                'If set to True then Reset the Current Value
        FunctionValue = ValueToSet            'Reset the value
        ValueResults = FunctionValue          'Return Results as a parameter
 
    CASE ELSE                                 ' If set to False, or -1 Then Get Current Value
        ValueResults = FunctionValue          'Return Results as a parameter
   END SELECT
FUNCTION = %False                             'Return if Function Failed
END FUNCTION

[John Petty]

Remember that if the variable is a string then VARPTR will remain constant but STRPTR may change if you change the contents.