[fpc-devel] restbase.pp LoadFromJSON calling StopRecordPropertyChanges;

[Michael Van Canneyt]

On Sat, 14 Jan 2023, Wayne Sherman wrote:

> On Fri, Jan 13, 2023 at 11:48 PM Michael Van Canneyt wrote:
>> Markpropertychanged is called in the setter of the properties generated by
>> the code generator: Check all generated units.
>
> Thanks for your explanations, it is getting more clear how modified
> property tracking is being used.
>
> More clarification please.  MarkPropertyChanged offsets the property
> changed index (to TBits) by the ClassParent total property count, but
> IsPropertyModified does not take this offset into account.  Consider
> this example:
>
> TBaseObject --> TGoogleBaseObject --> TSchema --> TMySchema
> TBaseObjectClass = Class of TBaseObject;
>
> If the object is TMySchema, in GetParentPropCount the TBits index gets
> offset by (see reference code below):
>  TBaseObjectClass(TSchema).GetTotalPropCount;
> If the object is TSchema, the TBits index gets offset by:
>  TBaseObjectClass(TGoogleBaseObject).GetTotalPropCount;
>
> Questions:
> 1) Since the ClassParent is always cast as TBaseObjectClass isn't this
> the same as just TBaseObjectClass(Self.ClassType)?

No. The method is virtual, so the actual descendant's method is called.

>
> 2) Doesn't each object already have the parent properties included in
> its own properties by inheritance?

Why this question ? 
An object does not know the property count of the parent.


>
> 3) Why does MarkPropertyChanged offset the index and
> IsPropertyModified does not take the offset into account?

They should be the same. I don't remember why I created the two methods
differently.

Michael.

>
> Reference for above questions:
>
> class function TBaseObject.GetParentPropCount: Integer;
> begin
>  if (ClassParent=TBaseObject) or (ClassParent=Nil) then
>    Result:=0
>  else
>    Result:=TBaseObjectClass(ClassParent).GetTotalPropCount;
> end;
>
> procedure TBaseObject.MarkPropertyChanged(AIndex: Integer);
> begin
>  If Assigned(FBits) then
>    FBits.SetOn(GetParentPropCount+(AIndex shr IndexShift));
> end;
>
> function TBaseObject.IsPropertyModified(Info: PPropInfo): Boolean;
> begin
>  Result:=Not Assigned(FBits) or FBits.Bits[Info^.NameIndex]
> end;
>
> </end reference code>
>