Setting fixed height for iOS8 today extension using auto layout

Question

I am trying to implement a simple today widget which contains a single label with fixed height.

In the documentation it says:

If a widget has additional content to display, you can rely on Auto Layout constraints to adjust the widget’s height as appropriate.

However I keep getting "Unable to simultaneously satisfy constraints" warnings.

Here is what I tried:

1. Create a new "Today Extension" target, it creates the storyboard with a "Hello World" label and view controller.
2. Set height constraint to "Hello World" label.

And when I run I get:

2014-09-18 21:13:07.123 TestWidget[23381:871330] 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:0x7f87c31126d0 V:[UILabel:0x7f87c3113230'Hello World Fixed Height'(21)]>",
    "<NSLayoutConstraint:0x7f87c30235b0 V:[_UILayoutGuide:0x7f87c30222b0]-(NSSpace(8))-[UILabel:0x7f87c3113230'Hello World Fixed Height']>",
    "<NSLayoutConstraint:0x7f87c3023600 V:[UILabel:0x7f87c3113230'Hello World Fixed Height']-(NSSpace(8))-[_UILayoutGuide:0x7f87c3022f00]>",
    "<_UILayoutSupportConstraint:0x7f87c3021980 V:[_UILayoutGuide:0x7f87c30222b0(0)]>",
    "<_UILayoutSupportConstraint:0x7f87c30218a0 V:|-(0)-[_UILayoutGuide:0x7f87c30222b0]   (Names: '|':UIView:0x7f87c3112f20 )>",
    "<_UILayoutSupportConstraint:0x7f87c3023360 V:[_UILayoutGuide:0x7f87c3022f00(0)]>",
    "<_UILayoutSupportConstraint:0x7f87c3023300 _UILayoutGuide:0x7f87c3022f00.bottom == UIView:0x7f87c3112f20.bottom>",
    "<NSLayoutConstraint:0x7f87c3326710 'UIView-Encapsulated-Layout-Height' V:[UIView:0x7f87c3112f20(628)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f87c31126d0 V:[UILabel:0x7f87c3113230'Hello World Fixed Height'(21)]>

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 am I doing wrong? What is the correct way to create a widget with fixed height using auto layout?

Answer 1

I found a way to remove those warnings by introducing a wrapper view, put all other views into this wrapper view and set a low priority to wrapper view's height constraint.