| Re: call_method [message #26569 is a reply to message #26480] |
Thu, 06 September 2001 21:31   |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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From: "David Fanning" <david@dfanning.com>
> P.S. Let's just say that if you wanted to enlighten us
> as to *why* you do this all the time, I would be all
> ears. :-)
Well, not all the time.
OK, to get specific, I have a general purpose graphics object called
MGHgrGraph, based on IDLgrView. MGHgrGraph has a method called NewAtom that
creates a graphics atom and attaches it to the graphics tree. Creating an
object graphics plot usually consists of creating an MGHgrGraph then calling
NewAtom several times. The function form of the NewAtom method returns a
reference to the atom; the procedure form doesn't. Most of the time I don't
need the reference, so I call the procedure form; sometimes I do need the
reference, so I call the function form. (The code is a bit more readable
when the procedure form is used, I think.)
The function definition contains all the code to implement NewAtom. The
procedure form is a wrapper that looks like this
pro MGHgrGraph::NewAtom, P1, P2, P3, P4, RESULT=result, _EXTRA=extra
compile_opt IDL2
case n_params() of
0: result = self->NewAtom( _EXTRA=extra )
1: result = self->NewAtom( P1, _EXTRA=extra )
2: result = self->NewAtom( P1, P2, _EXTRA=extra )
3: result = self->NewAtom( P1, P2, P3, _EXTRA=extra )
4: result = self->NewAtom( P1, P2, P3, P4, _EXTRA=extra )
endcase
end
The RESULT keyword is for when I change my mind & decide I *do* want the
object reference after all.
> It must have something to do with all those sheep. :-)
I don't farm sheep but do I farm olive trees. They have the advantage that
they don't move around so much, but on the other hand they aren't as warm &
cuddly.
---
Mark Hadfield
m.hadfield@niwa.cri.nz http://katipo.niwa.cri.nz/~hadfield
National Institute for Water and Atmospheric Research
--
Posted from clam.niwa.cri.nz [202.36.29.1]
via Mailgate.ORG Server - http://www.Mailgate.ORG
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