[fpc-devel] TField.OldValue

[michael.vancanneyt at wisa.be]

On Thu, 9 Jun 2011, LacaK wrote:

> Hi *,
> I have 2 questions, which I divide into 2 emails.
>
> 1st is about TField.OldValue and Delphi compatibility. Please look at small 
> attached program (for SQLite3).
>
> In Delphi (with TClientDataSet and dbExpress) outputs:
> 1. Field.OnValidate: OldValue=N; Value=N; NewValue=N
> 2. Field.OnChange: OldValue=O; Value=N; NewValue=N
> 3. BeforePost: OldValue=O; Value=N; NewValue=N
> 4. AfterPost: OldValue=O; Value=N; NewValue=N
> 5. Before ApplyUpdates: OldValue=O; Value=N; NewValue=N
> 6. After ApplyUpdates: OldValue=N; Value=N; NewValue=N
>
> In FPC:
> 1. Field.OnValidate: OldValue=N; Value=N; NewValue=N
> 2. Field.OnChange: OldValue=null; Value=N; NewValue=N
> 3. BeforePost: OldValue=null; Value=N; NewValue=N
> 4. AfterPost: OldValue=O; Value=N; NewValue=N
> 5. Before ApplyUpdates: OldValue=O; Value=N; NewValue=N
> 6. After ApplyUpdates: OldValue=null; Value=N; NewValue=N
>
> As you can see, there are differences in 2,3,6, where in FPC OldValue is NULL 
> but in Delphi is it "old value".
> Dou you think, that it is bug ? (at least it makes impossible compare 
> OldValue and Value in BeforePost event handler and take some action when some 
> field changes)

At least it is a bug in 2,3. 
The OldValue should IMHO be available till the Post statement.
After that, it is subject to debate.

Michael.