iphone - Can I use size classes in xib file in IOS 8.1? -

my app universal app, i.e. app iphone_portrait , ipad_landscape.

i searched lot how deal iphone , ipad, , found can make add adaptive using size classes, after ios 8 size classes

my question :

1. is solution best one, if design wan't simple?
2. i have lot of xib files in app. can use size classes in case? or need 2 xib 1 iphone, 1 ipad?

thanks.

yes can use size class , autolayout. see following screen shot there tick mark on right side in file inspector.