You get this issue because when setting a subview from within UIStackView to hidden, it will first constrain its height to zero in order to animate it out.
I was getting the following error:
2015-10-01 11:45:13.732 <redacted>[64455:6368084] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSLayoutConstraint:0x7f7f5be18c80 V:[UISegmentedControl:0x7f7f5bec4180]-(8)-| (Names: '|':UIView:0x7f7f5be69d30 )>",
"<NSLayoutConstraint:0x7f7f5be508d0 V:|-(8)-[UISegmentedControl:0x7f7f5bec4180] (Names: '|':UIView:0x7f7f5be69d30 )>",
"<NSLayoutConstraint:0x7f7f5bdfbda0 'UISV-hiding' V:[UIView:0x7f7f5be69d30(0)]>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x7f7f5be18c80 V:[UISegmentedControl:0x7f7f5bec4180]-(8)-| (Names: '|':UIView:0x7f7f5be69d30 )>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
What I was trying to do, was to place a UIView within my UIStackView that contained a UISegmentedControl inset by 8pts on each edge.
When I set it to hidden, it would try to constrain the container view to a zero height but because i have a set of constraints from top to bottom, there was a conflict.
To resolve the issue, I changed my 8pt top an bottom constraints priority from 1000 to 999 so the UISV-hiding constraint can then take priority if needed.