Why the preview don't layout

i made the constrain already
this happens with only xcode8
i haven’t met it with older version

It could be a bug in Xcode 8, or maybe there is something wrong with your constraints. It’s hard to say for me because I don’t know what your constraints are.

i’d rather believe something wrong with my constraints, but the app’s layout is work good at simulator. emm…
maybe this will show something?

Yeah, I don’t see anything wrong in those screenshots…

fine, after all, my app works good.
i should ignore it >.<
and thank you for help, thank your book~
i think i’ll buy the whole :blush: