Hi Pere,
A variant of my first program answering your 2nd question.
void pere2() {
// example illustrating the use of TMethodCall
//create a TMethodCall for the TLine constructor
TMethodCall mc,mcdraw;
mc.InitWithPrototype(TLine::Class(),"TLine","double,double,double,double");
Long_t l;
TRandom r;
char params[100];
//draw 100 lines
for (int i=0;i<100;i++) {
sprintf(params,"%f,%f,%f,%f",r.Rndm(),r.Rndm(),r.Rndm(),r.Rndm());
mc.Execute(0,params,l);
TLine *line = (TLine*)l;
line.Draw();
}
}
Rene Brun
Pere Mato wrote:
>
> Hi Rene,
>
> Thanks very much. I think this answers my questions 1 and 3, but still I
> do not see how to return a value that is not a int, float or char*. The
> TMethodCall::Exec() only offers these posibilities. For example how I get
> the TCanvas::GetFrame() executed that is supossed to return a TFrame*.
> Should I get the int and cast it to TFrame*? Do you never return a complex
> object by value in ROOT?
>
> Pere
>
> > -----Original Message-----
> > From: Rene.Brun@cern.ch [mailto:Rene.Brun@cern.ch]
> > Sent: 18 January 2002 09:51
> > To: Pere Mato
> > Cc: Roottalk
> > Subject: Re: [ROOT] Questions on using the Meta Classes
> >
> >
> > Hi Pere,
> >
> > The answer to your 3 questions is to use TMethodCall. A small example:
> > void pere() {
> > // example illustrating the use of TMethodCall
> >
> > void pere() {
> > // example illustrating the use of TMethodCall
> >
> > //create a TMethodCall for the TLine constructor
> > TMethodCall mc,mcdraw;
> >
> > mc.InitWithPrototype(TLine::Class(),"TLine","double,double,double,
> > double");
> > mcdraw.InitWithPrototype(TLine::Class(),"Draw","const char*");
> > Long_t l,ldraw;
> > TRandom r;
> > char params[100];
> > //draw 100 lines
> > for (int i=0;i<100;i++) {
> > sprintf(params,"%f,%f,%f,%f",r.Rndm(),r.Rndm(),r.Rndm(),r.Rndm());
> > mc.Execute(0,params,l);
> > mcdraw.Execute((TLine*)l," ",ldraw);
> > }
> > }
> >
> > In the InitWithPrototype call, you can specify any complex type:
> > - basic type,
> > - class
> > - pointer, etc
> >
> > to pass a pointer, simply encode the value of the pointer, eg for a TLine*
> > sprintf(params,"(TLine*)0x%x",line); //where line is a TLine*
> >
> > Rene Brun
> >
> > Pere Mato wrote:
> > >
> > > Hi All,
> > >
> > > I am trying to make an exercise of interfacing ROOT with
> > Python using the
> > > API provided by the ROOT Meta classes (TClass, TMethod,
> > TDataMember, etc.)
> > > and I have several questions:
> > >
> > > - How to call a constructor with arguments. The method
> > TClass::New() calls
> > > only the default constructor. I naively tried to call the class
> > constructor
> > > method as a normal method using TObject::Execute(...)
> > immediately after the
> > > object has been created with TClass::New() but it does not seem to work.
> > >
> > > - How to get the return value of a function/method call. The method
> > > TObject::Execute(...) does not give you this possibility. Also
> > the method
> > > TMethodCall::Execute(...) allows only to return either a long,
> > double or a
> > > string but nothing else.
> > >
> > > - How I can pass a "complex" data type as an argument to a method. In
> > > particular, how I can give a TObject* as argument. The way I
> > understand the
> > > method TObject::Execute() works is by constructing a string with comma
> > > separated argument values. In the case of being within the CINT
> > interpreter
> > > it seems that you can pass the name of a CINT variable pointing to your
> > > complex data type. But if you are not in CINT, which is exactly
> > my case I do
> > > not see how I can do it.
> > >
> > > Thanks in advance for any hint or suggestion,
> > >
> > > ------------------------------------------------------------
> > > Pere Mato CERN, EP Division, CH 1211 Geneva 23, Switzerland
> > > e-mail: Pere.Mato@cern.ch tel: +41 22 76 78696
> > > fax: +41 22 76 79425 gsm: +41 79 20 10855
> >
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