I already implanted a code that allows 99% of the font of my application to some specific fonts:
@implementation UILabel(SizedFontName) //APPEARANCE
- (void)setSizedFontName:(id)test UI_APPEARANCE_SELECTOR
{
    NSString *fontName = self.font.fontName;
    CGFloat fontSize = self.font.pointSize;
    if ([[fontName lowercaseString] rangeOfString:@"bold"].location != NSNotFound || [[fontName lowercaseString] rangeOfString:@"fb"].location != NSNotFound)
    {
        self.font = [UIFont fontWithName:nameFontBold size:fontSize];
    }
    else if ([[fontName lowercaseString] rangeOfString:@"italic"].location != NSNotFound)
    {
        self.font = [UIFont fontWithName:nameFontItalic size:fontSize];
    }
    else
    {
        self.font = [UIFont fontWithName:nameFontRegular size:fontSize];
    }
}
@end
I call it with the line:
//APPEARANCE
    [[UILabel appearance] setSizedFontName:nil];  
That works well but I would like to have the same to complete my application with the alert views that seems to escape to that piece of code...
Thanks in advance.