UILabel visible part of text

You could use a category to extend NSString and create the method you mention

@interface NSString (visibleText)

- (NSString*)stringVisibleInRect:(CGRect)rect withFont:(UIFont*)font;

@end

@implementation NSString (visibleText)

- (NSString*)stringVisibleInRect:(CGRect)rect withFont:(UIFont*)font
{
    NSString *visibleString = @"";
    for (int i = 1; i <= self.length; i++)
    {
        NSString *testString = [self substringToIndex:i];
        CGSize stringSize = [testString sizeWithFont:font];
        if (stringSize.height > rect.size.height || stringSize.width > rect.size.width)
            break;

        visibleString = testString;
    }
    return visibleString;
}

@end