>> That's right. And for that you can test the object itself (which is >> actually an alias). But once you put an object into a variable you need >> another way to indicate whether its valid or not.
I agree, Bill. It could be very usefull, if there was a function in MapBasic that actual could test whether an object was legal or not/exists or was null, or what ever you want to call this state. This is especially usefull when you have a function, that expects to get an object and also returns an object. How would you handle this situation ? What you make sure that you don't call the function with a not existing object, or could in some way handle the problem inside the function in a smart manner without corupting the table ? I tend to check before calling the funtion, but would love to hear about a solution to the second if possible. Peter Horsbøll Møller GIS Developer, MTM Geographical Information & IT COWI A/S Odensevej 95 DK-5260 Odense S. Denmark Tel +45 6311 4900 Direct +45 6311 4908 Mob +45 5156 1045 Fax +45 6311 4949 E-mail [EMAIL PROTECTED] http://www.cowi.dk/gis "For enden af regnbuen..." - hvordan kommer man dertil og er det overhovedet muligt? Læs mere om årets MapInfo konference på www.cowi.dk/mapinfokonference -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill Thoen Sent: Friday, July 28, 2006 5:39 PM To: Spencer Simpson Cc: mapinfo-l@lists.directionsmag.com Subject: Re: [MI-L] MAPBASIC Object or not Object? Spencer Simpson wrote: >No, I've found that aliases (especially objects) can act strangely if >you try to extract their values more than once between two successive fetches. >Maybe newer versions of MapInfo are more robust, but it conditioned me >to always fetch aliases into variables back in the 1990s. > > I'd have to say, "Prove it." IMHO, that's a superstition that you develpoed as you were learning and now it's just a habit. It's similar to the superstition that using defined constants is not safe. >Using "degenerate" objects to simulate null objects is useful, but it >doesn't help fetching them from a table, because you can't guarantee >that a row didn't have its object deleted. > > That's right. And for that you can test the object itself (which is actually an alias). But once you put an object into a variable you need another way to indicate whether its valid or not. _______________________________________________ MapInfo-L mailing list MapInfo-L@lists.directionsmag.com http://www.directionsmag.com/mailman/listinfo/mapinfo-l _______________________________________________ MapInfo-L mailing list MapInfo-L@lists.directionsmag.com http://www.directionsmag.com/mailman/listinfo/mapinfo-l
