Find out who adds a specific auto layout constraint

Question

How do I find out who adds a specific auto layout constraint?

Because I'm seeing some constraints which I'm certain I did not add.

Did you set `translatesAutoresizingMaskIntoConstraints` to `false`? — BallpointBen, Mar 09 '17 at 16:58
Start using storyboards and xibs to define constraints. You will see that many such problems will go away. A constraint can be created from autoresizing mask for example. Sometimes a constraint can be added automatically when the current constraint are not suficient. — Sulthan, Mar 09 '17 at 18:14
@matt, "And the generic answer" is [this](http://stackoverflow.com/a/42807700/865175). Now please remove your downvote. — Iulian Onofrei, Mar 15 '17 at 10:55
I'm not interested in your book. 1. A symbolic breakpoint would stop at __exactly__ where it was created so you'll see "who added it". 2. If you set the `accessibilityIdentifier` for your `UIView`s, you could distinguish them from others so you'll yet again know "who added" the constraints. You can also edit questions. Now please remove your downvote. — Iulian Onofrei, Mar 15 '17 at 13:38

score 1 · Answer 1 · answered Mar 09 '17 at 16:43

1

In Swift you could look at var identifier: String?. If it starts with NS then it was added by iOS.

A constraint’s identifier is available in its description. Identifiers that start with NS are reserved by the system.

answered Mar 09 '17 at 16:43

aahrens

5,522
7
39
63

And if doesn't? – Iulian Onofrei Mar 09 '17 at 18:23
If the identifier is blank it's likely a constraint you added via code, a storyboard, or XIB – aahrens Mar 09 '17 at 19:26

score 0 · Accepted Answer · edited May 23 '17 at 11:46

If the layout is ambiguous or unsatisfiable, you can put a symbolic breakpoint on UIViewAlertForUnsatisfiableConstraints.

You can add a Debugger Command containing po [[UIWindow keyWindow] _autolayoutTrace] for Objective-C or expr -l objc++ -O -- [[UIWindow keyWindow] _autolayoutTrace] for Swift which automatically prints the UIView hierarchy, as desribed in this article.
You can also use po $r15 in the debugger to print the "details description of constraint that is broken" or po $r14 for "more detailed description of all constraints added in addition to breaking constraint", as described in this article.

If not, you can set the accessibilityIdentifier for your UIView (or directly in the IB) which will show up in the previous expressions' results (and other places too) instead of the string UIView.

Find out who adds a specific auto layout constraint

2 Answers2