Tips and Tricks

Using UIView+AutoLayout with Interface Builder

You may want to use a combination of an Interface Builder file (nib/xib/storyboard) that specifies some constraints along with additional constraints added in code using the UIView+AutoLayout API. In general, this is a fine way of doing things.

Be aware that when using Xcode 5, you are allowed to have ambiguous layouts in Interface Builder, and at build time (without telling you) Xcode will automatically create and add in the necessary constraints to make your layout fully specified. This can cause problems for you at runtime if these auto-generated IB constraints end up conflicting with constraints you create and add in code.

To solve this issue, you'll need to create placeholder constraints for any ambiguous parts of your layout in Interface Builder. These placeholder constraints are removed from your layout at build time, and also prevent the auto-generated IB constraints from being added in their place.

Debugging constraint issues

If you're having an issue with a constraint being broken due to a conflict (check your console output), one of the best ways to debug is to comment out constraints one-by-one until the issue disappears. (Alternatively, you can comment all the constraints out and add them back in one-by-one until the issue appears.) This will help you isolate the particular constraint(s) that are causing the problem.