My view does not translate its autoresizing mask. But you are confirming my suspicion that some issue is lurking here. I wonder if it wouldn't be better if some kind of runtime warning were issued when I do this sort of thing...
It would help me if you could suggest a method call that would exercise the constraint system, e.g. perhaps causing the frame to snap back to height 36, thus proving to the student that this behavior is problematic. I tried things like layoutSubviews and layoutIfNeeded but nothing happened. Thx - m. On Nov 26, 2012, at 12:37 PM, Kyle Sluder <[email protected]> wrote: > On Mon, Nov 26, 2012, at 10:46 AM, Matt Neuburg wrote: >> I have noticed by experimentation that if I have a layout constraint on a >> view that sets its height at (say) 36, I can later change the view's >> frame in code to set its height at (say) 50. The view's height does >> visibly change, but logging proves that the layout constraint does not >> change. >> >> (1) How can this be? The view would appear to be violating its own layout >> constraint. > > Constraints don't care about the view's frame. They only care about each > other. When the constraint system runs, it calls -setFrame: on the > views. It never pays attention to what values they have. > >> (2) More important: Is this a bad situation? In other words, once I've >> decided to use layout constraints at all, must I then use them for >> everything and avoid frame/bounds? Can something bad happen later because >> of this conflict? > > Yes, this is a bad situation. You should use constraints. You run the > risk of your views being resized whenever the next layout pass is > triggered. > > Additionally, my statement above is a lie: constraints don't care about > the current frame of your views, but if a view is set to translate its > autoresizing mask into constraints, and either the X or Y dimension is > not fully stretchable, it updates these constraints' constants with the > values from the frame whenever the frame changes size. > > So that means you CAN cause a conflict by calling -setFrameSize: on a > view if you're still mixing constraints with autoresizing-mask-based > layout. > > --Kyle Sluder -- matt neuburg, phd = [email protected], http://www.apeth.net/matt/ pantes anthropoi tou eidenai oregontai phusei Programming iOS 5! http://shop.oreilly.com/product/0636920023562.do RubyFrontier! http://www.apeth.com/RubyFrontierDocs/default.html TidBITS, Mac news and reviews since 1990, http://www.tidbits.com _______________________________________________ Cocoa-dev mailing list ([email protected]) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [email protected]
