Re: Loops
Re: Loops
- Subject: Re: Loops
- From: Michael <email@hidden>
- Date: Fri, 1 Feb 2008 04:42:29 -0800
Thank you Neil.
On Feb 1, 2008, at 4:32 AM, Neil Faiman wrote:
On Feb 1, 2008, at 1:59 AM, Michael wrote:
Question 1) Will AS "wait" for the action to be completed eg
moving a file
2) How does it know that the action has been successfully
transacted ( assuming the answer to 1 is yes)
3) Is it ever possible for a loop to "outpace" it's asked for
action.
1) In general, when a script tells an application to do something,
it sends a message to the application, and waits for the application
to send back an "I'm done, and here's the result" message before it
continues.
2) The script also starts a timer when it sends the message to the
application. If the timer runs out before a message comes back, the
script gets an "application timed out" error. (The default timer is
60 seconds; you can change that if you know that some operation is
likely to take a long time.) The script can catch the time-out error
with an error handler and can continue executing or do something else.
3) The script can also use the "ignoring application responses"
modifier to just send the message to the application, and not bother
waiting for a reply. In this case, the script has no direct way of
knowing when or if the operating has completed, but it can use
indirect methods to check (for example, looking for the file in the
destination folder).
4) In theory, if you don't use "ignoring application responses" a
script shouldn't be able to "get ahead of" the application, since it
always waits for the application to complete an operation before it
does the next thing (see 1). But practice doesn't always match
theory. A few days ago I looked at the problem of enabling or
disabling fonts in Font Book. It turned out that a loop over all the
fonts, telling Font Book to enable each of them, died after enabling
only one or two; but inserting a one second delay in the loop fixed
the problem. We never figured out the precise cause; but it
certainly sounds like Font Book was returning to the application
before it had really finished the enabling a font, so that sometimes
it tripped over itself when it was asked to enable the next font
before it had finished the previous one.
Still, the normal way to script would be to assume that following a
script statement, any operations it requested will be complete, and
not to worry about weird cases like (4) until they happen.
Regards,
Neil Faiman
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