I've just upgraded to xcode 8 swift 3 and the whole layout of my project is a mess. I'm trying to change constraints but is not taking effect in preview like last version. I've follewed the same procedure I've used to Xcode 7.3. Are there something new that I don't know ?
After some more searching I found that this a bug. This workaround solved https://stackoverflow.com/a/39653512/2238515 my issue. On the other hand is waiting for an update from Apple