Python4Delphi: Returning a python object in a function. (DelphiWrapper)

Question

I am using python4delphi. How can I return an object from a wrapped Delphi class function?

Code Snippet:

I have a simple Delphi Class that I wrapped to Python Script, right?

TSimple = Class
Private
  function getvar1:string;
Public    
Published
  property var1:string read getVar1;
  function getObj:TSimple;
end;
... 
function TSimple.getVar1:string;
begin
  result:='hello';
end;
function TSimple.getObj:TSimple;
begin
  result:=self;
end;

I made the TPySimple like the demo32 to give class access to the Python code. My Python module name is test.

TPySimple = class(TPyDelphiPersistent)
  // Constructors & Destructors
  constructor Create( APythonType : TPythonType ); override;
  constructor CreateWith( PythonType : TPythonType; args : PPyObject ); override;
  // Basic services
  function  Repr : PPyObject; override;

  class function  DelphiObjectClass : TClass; override;
end;
...

{ TPySimple }

constructor TPySimple.Create(APythonType: TPythonType);
begin
  inherited;
  // we need to set DelphiObject property
  DelphiObject := TSimple.Create;
  with TSimple(DelphiObject) do begin
  end;
  Owned := True; // We own the objects we create
end;

constructor TPySimple.CreateWith(PythonType: TPythonType; args: PPyObject);
begin
  inherited;
  with GetPythonEngine, DelphiObject as TSimple do
    begin
      if PyArg_ParseTuple( args, ':CreateSimple' ) = 0 then
        Exit;
    end;
end;

class function TPySimple.DelphiObjectClass: TClass;
begin
  Result := TSimple;
end;

function TPySimple.Repr: PPyObject;
begin
  with GetPythonEngine, DelphiObject as TSimple do
    Result := VariantAsPyObject(Format('',[]));
    // or Result := PyString_FromString( PAnsiChar(Format('()',[])) );
end;

And now the python code:

import test

a = test.Simple()
# try access the property var1 and everything is right
print a.var1
# work's, but..
b = a.getObj();
# raise a exception that not find any attributes named getObj.
# if the function returns a string for example, it's work.

Answer 1

I have run into the same problem while using DelphiWrapper.

First, enable RTTI using {$METHODINFO ON} will prevent exception:

raise a exception that not find any attributes named getObj.

Write TSimple class like this:

{$METHODINFO ON}
TSimple = Class
Private
  function getvar1:string;
Public    
Published
  property var1:string read getVar1;
  function getObj:TSimple;
end;
{$METHODINFO OFF}

Now getObj function returns a value -- an Integer!!

I'll show you guys what I did. I modified Demo32:

Unit1.pas:

TPoint = class(TPersistent)
private
  fx, fy : Integer;
  fName : String;
public
  constructor Create();
  procedure OffsetBy( dx, dy : integer );
  function MySelf: TPoint;  //**access self using function**
published
  property x : integer read fx write fx;
  property y : integer read fy write fy;
  property Name : string read fName write fName;
  property MySelf2: TPoint read MySelf; //**access self using property**
end;

Python code in Memo1.Lines:

import spam

p = spam.Point(2, 5)

b = p.MySelf()  //**using function**
print 'Using MySelf: ', type(b), b
c = p.MySelf2   //**using property**
print 'Using MySelf2: ', type(c), c

Then it gives a result like this:

Using MySelf:  <type 'int'> 31957664
Using MySelf2:  <type 'Point'> (2, 5)

The function returns an int, that's wired. Maybe it's a pointer to a TPoint object incorrectly wrapped by DelphiWrapper.

Finally I found a compromise way in Demo8 using "AddMethod". Not beautiful at all!! But it works.