Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!jdevoto
From: jdevoto@Apple.COM (Jeanne A. E. DeVoto)
Newsgroups: comp.sys.mac.hypercard
Subject: Re: Checking for card existance?
Summary: use the result
Keywords: HyperCard, Booga-Booga-Booga
Message-ID: <40749@apple.Apple.COM>
Date: 4 May 90 22:02:23 GMT
References: <903@gistdev.gist.com>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 28

In article <903@gistdev.gist.com> andy@gistdev.gist.com (Andy Warinner) writes:
>I have a field that stores the id of a card.  Is there any way to 
>check that the id stored actually exists?  For example:
>
>	-- bkgnd field "cardPtr" holds card id
>	if verifyCard(bkgnd field "cardPtr")
>		then go to card id (bkgnd field "cardPtr")
>		else answer "You screw up!"

If you try to go to a non-existent card from a script, the result function
will return a non-empty value. The following will do the check:

  go card ID XXX
  if the result is not empty then
    -- do failure procedure
  else
    -- do success procedure
    -- if you just wanted to check for existence, not go to the card,
    -- you can put a "go recent card" in here to get back to where you
    -- were.
  end if
-- 
========= jeanne a. e. devoto ========================================
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