[fpc-pascal] Changing iterator usage pattern in FCL-STL

Sven Barth pascaldragon at googlemail.com
Sun Nov 8 22:22:54 CET 2015

On 08.11.2015 19:38, leledumbo wrote:
> FCL-STL from the start has different iterator usage pattern compared to
> existing containers (say a TSQLQuery). i.e. the common pattern is:
> It := SomeContainer.Iterator;
> while not It.EOF do begin
>    ...
>    It.Next;
> end;
> instead, it uses:
> It := SomeContainer.Iterator;
> repeat
>    ...
> until not It.Next;
> Examining the iterator code, I can see that the latter has at least the
> following disadvantage:
> One must add additional guard before executing repeat-until to make sure
> that the container has at least 1 data. Otherwise, Next in until expression
> will trigger EAccessViolation.
> I would like to change the pattern to follow existing one. However, FCL-STL
> has been available for some time now that changing the pattern will break
> existing code. How do you think I should proceed on this one?

I'd say don't change. In my opinion the need to restructure one's code 
outweighs that disadvantage. If anything then add a for-in compatible 
iterator like was done for TVector<>.


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