DWScript: exposing and returning an object to script from Delphi function?

Question

In my Delphi (2010) code I have a class TImageItem, which I have exposed to DWScript via:

dwsUnit.ExposeRTTI(TypeInfo(TImageItem),[eoNoFreeOnCleanup, eoExposePublic]);

In dwsUnit I have declared a function to get a TImageItem from the Delphi side:

function GetImage: TImageItem;

and on the Delphi side:

procedure TFScript.dwsUnitFunctionsGetImageEval(info: TProgramInfo);
begin
    ...
    // (Item is a TImageItem and not nil)
    Info.ResultAsVariant := TdwsRTTIVariant.FromObject(Item);
end;

However, when I run a script starting like:

var Item: TImageItem;
Item := GetImage;
...

I get an EScriptError during the GetImage call with the message "Object already destroyed".

What am I doing wrong? Am I exposing the object or returning it incorrectly?

AndersMelander · Accepted Answer · 2015-11-14 19:25:57Z

2

I don't know about ExposeRTTI, as I've never used it, but I would do it like this:

procedure TFScript.dwsUnitFunctionsGetImageEval(info: TProgramInfo);
begin
  ...
  // (Item is a TImageItem and not nil)
  Info.ResultAsVariant := Info.Vars[Info.ResultVars.TypeSym.Name].GetConstructor('Create', Item).Call.Value;
end;

answered Nov 14, 2015 at 19:25

AndersMelander

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