Check multiple screens and mirroring

CheckScreensMirroring.mm

for (UIScreen *screen in [UIScreen screens]) 
{
    if ([screen respondsToSelector:@selector(mirroredScreen)] && 
        [screen mirroredScreen] == [UIScreen mainScreen]) 
    {
        // The main screen is being mirrored.
    }
    else 
    {
        // The main screen is not being mirrored, or
        // you are not running on a compatible device.
    }
}