| Re: Keywords/Parameters and Common Blocks [message #36847] |
Fri, 31 October 2003 09:53  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Nuno Oliveira writes:
> Sometimes I want use keyword variables (or parameters) of a function or
> procedure in routines not only in the main program (of the
> function/procedure) but also on subroutines (as often happens with routine
> events). Intuitively I put the keyword variables on a block shared with the
> subroutine that I also want to use those variables. But it gives an error;
> that I can't remember now. It forces me to create new variables where I put
> the contents of the keyword variables, and then those variables I created in
> the program I can share with subroutines with common block.
>
> Is there a way that I can achieve this without making as many attributions
> as many keyword variables I want to share in COMMON blocks?
I get the impression here that you are writing widget
programs. If so, you do NOT want to be using COMMON blocks. :-)
Use an "info" or "state" structure instead. See any widget
program on my web page for an example of how this is done.
Typically, if you want to collect keywords for routines,
you store them in your info structure so they can be used:
PRO MyProgram, Color=color, Linestyle=linestyle
IF N_Elements(color) EQ 0 THEN color = 'red'
IF N_Elements(linestyle) EQ 0 THEN linestyle = 1
info = { color:color, linestyle:linestyle }
Widget_Control, tlb, Set_UValue=info
etc.
END
Then, you can use them in an event handler:
PRO MyProgramEvents, event
Widget_Control, event.top, Get_UValue=info
MYPLOT, findgen(11), Color=info.color, LineStyle=info.linestyle
END
Sometimes you want to collect "extra" keywords, or keywords
that you might want to use, but don't want to take the time
to define. Then you might use a pointer to store these "extra"
keywords:
PRO MyProgram, _Extra=extra
IF N_Elements(extra) EQ 0 THEN $
extra = Ptr_New(/Allocate_Heap) ELSE $
extra = Ptr_New(extra)
info = { extra=extra}
Widget_Control, tlb, Set_UValue=info
etc.
END
Then, use them like this:
PRO MyProgramEvents, event
Widget_Control, event.top, Get_UValue=info
MYPLOT, findgen(11), _Extra=*info.extra
END
Just be sure you free your pointers in the CLEANUP procedure
you will write for your widget program. :-)
Cheers,
David
--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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