beamlab@hscfvax.harvard.edu (D.McCallie) (02/18/88)
I need some hyperAdvice:
Is it possible to write an XCMD that remembers (internally)
data between invocations ? In other words, can I have states associated
with an XCMD so that the first call is treated differently from
subsequent calls ?
A similer question: is it possible to have external global
data that is shared between separate XCMDs, or must I send such
info back to HC itself (and thus require the stack author to
create stack "global" variables.
My preferred programming environment is LSC, but solutions
in any language would be appreciated. Thanks.
David McCallie
Children's Hospital
...harvard!hscfvax!{dpm, beamlab}
dpm@hscfvax.harvard.eduedmoy@violet.berkeley.edu (02/22/88)
In article <515@hscfvax.harvard.edu> beamlab@hscfvax.UUCP (850103@D.McCallie) writes: > Is it possible to write an XCMD that remembers (internally) >data between invocations ? In other words, can I have states associated >with an XCMD so that the first call is treated differently from >subsequent calls ? I haven't tried it yet, but if you create a resource (say of type 'DATA') in the stack, then you could do a GetResource() every time your XCMD is called. By making it nonpurgeable, the data would remain intacted. The latest state of the resource could be saved permenently by calling ChangedResource(). > A similer question: is it possible to have external global >data that is shared between separate XCMDs, or must I send such >info back to HC itself (and thus require the stack author to >create stack "global" variables. If the XCMDs shared the same knowledge of the resource, then the resource can be used to pass global info. Edward Moy Workstation Software Support Group University of California Berkeley, CA 94720 edmoy@violet.Berkeley.EDU ucbvax!violet!edmoy
ephraim@think.COM (ephraim vishniac) (02/22/88)
In article <515@hscfvax.harvard.edu> beamlab@hscfvax.UUCP (850103@D.McCallie) writes: > Is it possible to write an XCMD that remembers (internally) >data between invocations ? In other words, can I have states associated >with an XCMD so that the first call is treated differently from >subsequent calls ? > A similer question: is it possible to have external global >data that is shared between separate XCMDs, or must I send such >info back to HC itself (and thus require the stack author to >create stack "global" variables. > David McCallie > Children's Hospital > ...harvard!hscfvax!{dpm, beamlab} > dpm@hscfvax.harvard.edu What I would do is to use resources. (Be warned that I use resources for every blessed thing, however.) When your XCMD is invoked, do a GetNamedResource to find your data resource. Use a name for which collisions are very unlikely. Your own name, for example. If you don't find it, this must be the first call, so create the resource using a new resource ID. (There's a trap that spits out unused resource ID's for a given type, but I don't recall the name off the top of my head.) Any number of XCMD's can share data in this way: they just have to agree on the name and format of their common data resource. You can even save your data across HyperCard runs by marking the resource modified and making sure it gets saved as part of the stack. Ephraim Vishniac ephraim@think.com Thinking Machines Corporation / 245 First Street / Cambridge, MA 02142-1214