How can i get total, availabe and used RAM for iOS-Plattforms

Hello,

i´m developing an application and i use Xamarin.Forms (same layout and design) for iOS, Android and Windows Phone. But the functions of the App should be native like Android: getMemoryInfo(). Now the question is: How can i get total RAM, available RAM and used RAM for iOS?
Android and Windows Phone works already...

Regards,
AlKu