I really don't know why you want to do that, but there are some tricks to resize fields and buttons (I assume you want to do that)
You should be able to determine the screen size/native screen size so you can resize your CGRects for example.
http://stackoverflow.com/a/4779415/2826164https://stackoverflow.com/a/4779415/2826164
create an global function or variable to multiply your current width and heigth by, for example native width of 6+ = 1242*0,60306 = 750 native.
i'm not sure if you need 1080 or 1242 because of downscaling