//iOS7和其他系统版本跳转链接不一样- (void)clickUrl:(id)sender{    UIButton *bt = (UIButton *)sender;        NSString *str = @"";        if( ([[[UIDevice currentDevice] systemVersion] doubleValue]>=7.0))    {        str = [NSString stringWithFormat:@"itms-apps://itunes.apple.com/app/id%d",bt.tag];            }else    {        str = [NSString stringWithFormat:                         @"itms-apps://ax.itunes.apple.com/WebObjects/MZStore.woa/wa/viewContentsUserReviews?type=Purple+Software&id=%d",                         bt.tag ];    }    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:str]];}