Get device size on iOS device

deviceSize.m

- (CGSize)deviceSize
{
    CGSize size = [UIScreen mainScreen].bounds.size;
    if ([UIScreen instancesRespondToSelector:@selector(scale)] && [[UIScreen mainScreen] scale] > 1) {
        size = CGSizeMake(size.width * 2, size.height * 2); // Retina screenshot size support
    }
    return size;
}