Message: 7
Date: Fri, 23 Dec 2005 09:24:41 -0800
From: Jim Ault <[EMAIL PROTECTED]>
Subject: Re: Don't understand the meaning of "local"
To: How to use Revolution <[email protected]>
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset="US-ASCII"
"Local" is a deceptive descriptor. It is used (as a script local) to
control not only locality, but also persistence--it has both spacial
and temporal implications.
Perhaps it is the terminology used in the docs. More precisely, I think of
it as *handler local, *script local, and *global to Rev variables. The
handler local is the one that dies when exiting that handler. This allows
the same variable name (eg. tempVar) to be used without carry-over.
Also, 'set the itemDel to space' only applies to that running handler.
Entering another starts with the default itemDel, so this is a 'handler
local' setting. Important concept for front/back scripts and stacks in use
Globals are held by Rev and only die when either
delete variable gGlobalVar --is done
the user quits Revolution app.
This means that you could build a stack that is opened, sets some globals,
close with the 'destroyStack' as true, leaving the globals in RAM and
available to all stacks and sub stacks.
Obviously, the kinder, gentler stack design is to delete these variables on
closeStack.
Good questions.
Jim Ault
Las Vegas
Jim,
Good points.
The persistence of local SCRIPT variables that Chipp's earlier reply
clears up for me is handlers calling themselves (in x millisec or
whatever) in order to achieve asynchronous behavior ( i.e. not
monopolizing CPU time and allowing other uses of the CPU to seek
in.)
Unless the script remembers the local script variables (until the
next compiling of the code) then on the next call the handler will
not know what values to assign.
On way around this would be to include the value of the variable in
the call. For example in the following script the send message tells
the handler what the value of the variable should be after 20
millisec is up.
on mouseUp
put "" into field 1
checkPersistence 1
end mouseUp
on checkPersistence tNum
if tNum > 10 then exit checkpersistence
put tNum into field 1
send "checkPersistence tNum + 1" to me in 20 millisec
end checkPersistence
And there would be no need to include a script local variable.
But if checkPersistence look like this:
on checkPersistence
if tNum > 10 then exit checkpersistence
put tNum into field 1
add 1 to tNum
send "checkPersistence" to me in 20 millisec
end checkPersistence
It would not work unless tNum was declared earlier as a script local.
It's about time I'm getting these fundamental points straight. There
is a danger in learning RR on an as-needed basis.
Jim
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