This nugget is the third in a series of nuggets on Case structures. Today I will discuss Case structures that use String data types for their selector values. String selector The fact that we can wire strings to Case structure selectors is pretty handy. One common example would be running different cases of code for processing a file depending on its type. You can use the Get File Extension VI to get the file's extension, then use a Case structure to process the file differently, depending on its type: As you can see, a string Case structure allows for multiple values for cases, just like a numeric Case structure. Also, the use of a Default case for unknown strings is pretty common. Now in the case of this example, we don't have to worry about the casing of the file extensions, because the Get File Extension VI always returns file extensions in lower case. If you are in a situation where the casing of the string you want to match is unclear, you can use the Case Insensitive Match option on a string Case structure: I also like to use the fact that a double-double quote ( "" ) will match an empty string in a string Case structure. So instead of wiring a string to the Empty String/Path? function, and then wiring the Boolean output of that function to a Boolean Case structure, I just wire the string straight into the Case selector and have a "" case for the empty string. Finally, here are some oddities about string Case structures that you may need to know about someday: If you find yourself needing to match some of the special characters used in a string Case structure (like a double quote), you need to escape these with a backslash. So for a case matching a double quote, type \" in the frame selector. For a case matching a backslash, type \\. Most every other character I tried could be entered without the backslash, and instead just by enclosing it in quotes...for example, to match a comma, type "," in the frame selector. Matching ranges of characters doesn't quite work the way I expected it. For example, if I have a string Case structure with an a..c case, it matches a and b, but not c. I'm not sure why that is, but I'm guessing there's some sort of reasonable explanation. I can't think of any time I've needed to use ranges when matching strings, but if I ever do, I'll probably just play it safe and match ranges of ASCII character indices (and thus, use a numeric Case structure) instead of trying to match string ranges. You can convert strings to character arrays and vice-versa with the String to Byte Array and Byte Array to String functions, respectively. Now that I think about it, if you're just dealing with a single character, you could just use the Type Cast function. Message Edited by Darren on 03-09-2009 11:14 AM

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Darren's Weekly Nugget 03/09/2009

Ben wrote: Mike Porter also calls these "Catalog.vi"s.

Ah, Mike is showing his apple roots. I still remember using the CATALOG command on the Apple IIe to list the disk contents...

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Darren's Weekly Nugget 03/09/2009

Re: Darren's Weekly Nugget 03/09/2009