Setting both 'the result' and 'it' in a command

Trevor DeVore lists at
Mon Apr 21 09:44:13 EDT 2008

For anyone who has ever wanted to write a command that would set both  
'the result' and 'it' in the calling handler (like 'answer' does) try  
out this SetValueOfItInCaller handler below. I like to use it to write  
commands that can report any errors in 'the result' and return a value  
in 'it'.

It uses debugContext, debugDo and the executionContexts to pull it off  
so it is possible that the handler may stop working in future versions  
of the engine. But for now it works.

I've included the handler and an example of using it below. I posted a  
visual explanation of it here: < 


Trevor DeVore
Blue Mango Learning Systems    -

=== HANDLER ===

command SetValueOfItInCaller pValue
     global gTempStorageForItVar

     ## Store value in global
     put pValue into gTempStorageForItVar

     ## Store current debugcontext (debugger uses this)
     put the debugcontext into theContext

     ## the executionContexts is the list of handlers in the chain.
     ## This handler would be line -1.
     ## The handler that called this handler is -2.
     ## The handler that you want to set "it" in is -3
     set the debugcontext to line -3 of the executioncontexts

     ## Make the global gTempStorageForItVar available within context  
of handler we
     ## want to set "it" in. Then set it to the global var
     debugdo "global gTempStorageForItVar;put gTempStorageForItVar  
into it"

     ## restore debugcontext
     set the debugcontext to theContext

     ## cleanup
     delete global gTempStorageForItVar
end SetValueOfItInCaller

=== USAGE ===

on mouseUp pMouseBtnNo
     if pMouseBtnNo is 1 then
         put the result into theError

         if theError is empty then
             answer "Data returned is:" && it
             answer "Error getting data:" && the result
         end if
     end if
end mouseUp

command GetSomeDatabaseData
     SetValueOfItInCaller "some data" ## 'it' in caller will contain  
"some data"
     -- return empty
     return "error connecting to database" ## 'the result' will  
contain the error message
end GetSomeDatabaseData

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