How to check if UILabel is truncated?

Question

I have a UILabel that can be varying lengths depending on whether or not my app is running in portrait or landscape mode on an iPhone or iPad. When the text is

Answer 1

EDIT: I just saw my answer was upvoted, but the code snippet I gave is deprecated.
Now the best way to do this is (ARC) :

NSMutableParagraphStyle *paragraph = [[NSMutableParagraphStyle alloc] init];
paragraph.lineBreakMode = mylabel.lineBreakMode;
NSDictionary *attributes = @{NSFontAttributeName : mylabel.font,
                             NSParagraphStyleAttributeName : paragraph};
CGSize constrainedSize = CGSizeMake(mylabel.bounds.size.width, NSIntegerMax);
CGRect rect = [mylabel.text boundingRectWithSize:constrainedSize
                                         options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
                                      attributes:attributes context:nil];
if (rect.size.height > mylabel.bounds.size.height) {
    NSLog(@"TOO MUCH");
}

Note the calculated size is not integer value. So if you do things like int height = rect.size.height, you will lose some floating point precision and may have wrong results.

Old answer (deprecated) :

If your label is multiline, you can use this code :

CGSize perfectSize = [mylabel.text sizeWithFont:mylabel.font constrainedToSize:CGSizeMake(mylabel.bounds.size.width, NSIntegerMax) lineBreakMode:mylabel.lineBreakMode];
if (perfectSize.height > mylabel.bounds.size.height) {
    NSLog(@"TOO MUCH");
}