[Gambas-user] MoveFirst MoveNext etc

[Ron_1st]

On Thursday 09 April 2009, Jeff wrote:
> What is the thinking behind a Result.MoveFirst() and MoveNext()
> returning a false if a record is there?
> 
> So, to read round a result set I end up using a Boolean with a double
> negative:
> 
> noMoreRows = myResult.MoveFirst()
> WHILE NOT noMoreRows
>   PRINT myResult!id
>   noMoreRows = myResult.MoveNext()
> WEND 
> 
> I would have expected the MoveFirst() and MoveNext() return true if a
> record found, so I'm wondering why it's that way round.
> Or, is there a better loop structure to use so that it reads better?
> 
> 

The only logic I see is the way it is done in C/C++

If result returned is 0 means OK else the value other then
0 means the error code for the occured error.
-1 means i.e. syntax
-2 means i.e. invalid something

In C/C++ the IF THEN use a value instead the Basic boolean True/False
Symbolic 0 equals to False, other value to True 

Just in good old practice for Basic a question in IF ... THEN 
was/is always true.
So your way the next code is right
  IF myResults.MoveNext() then
    ' ok the movenext was OK
  ELSE
    ' oops a error
  ENDIF

For gambas in relation to the MoveXXX() this is reversed by Benoit.
It means with false ( equals to 0) there was no error

  IF myResults.MoveNext() then 
    ' returned not 0 (zero) 
    ' oops a error
  ELSE
    ' ok the movenext was OK
    ' return was 0 (zero)
  ENDIF

So you can use: 

Const NOERROR as boolean=false

  IF myResults.MoveNext() = NOERROR THEN 
    ' ok the movenext was OK
    ' return was 0 (zero)
  ENDIF

  

Personal I do not like the Gambas way, IMHO the myReult.MoveNext() 
should return TRUE if succes and FALSE when error occured.

I use now the method with NOERRO to get a clean Basic readable code.
NOERROR makes more sence then False here.


Best regards,

Ron_1st