String compare Objective-C

Question

I've been struggling with a simple comparison but I can't get it to work. I´m reading a XML file and I need to compare data from it in order to show the right picture.

http://www.cleaner.se/larm.xml (Example file for parsing)

I have tried things like:

if([aLarm.larmClass isEqualToString:@"A"])
    NSLog(@"same");
 else
    NSLog(@"Not same");

If I use: NSLog(aLarm.larmClass); console puts it out nicely as it should. What am I doing wrong?

Answer 1

You can use the NSString compare: methods. For example:

if ([myString caseInsensitiveCompare:@"A"] == NSOrderedSame ) {
    NSLog(@"The same");
} else {
    NSLog(@"Not the same.");
}

The result is an NSComparisonResult which is just an enum with types NSOrderedSame, NSOrderedAscending and NSOrderedDescending.

Check the documentation on the various compare: methods here.

Of course, if the receiver is actually an NSString, then isEqualToString: should also work. So if you're trying to compare a class name (aLarm.larmClass ??), then you can call:

if ([NSStringFromClass([aLarm class]) isEqualToString:@"A"] ) {
    NSLog(@"The same");
}

Answer 2

If the larmClass property is a string, make sure that it is actually one character in length (i.e. it doesn't have any leading or trailing whitespace that was accidentally included when parsing the XML). If the larmClass property truly is an NSString containing the letter ‘A’ then [aLarm.larmClass isEqualToString:@"A"] will return YES.

Do a:

NSLog(@"%u, %@", [aLarm.larmClass length], aLarm.larmClass);

and just make sure that it shows “1, A”.