Archive for the ‘iPad’ Category.

Unable to simultaneously satisfy constraints

All of a sudden, I started getting this error popping up in the console while developing my iOS 7 app:

2014-04-30 11:32:27.199 MyApp[4495:60b] 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) 
    "<NSAutoresizingMaskLayoutConstraint:0x1946a510 h=-&- v=-&- DetailTableView:0xe39ce00.width == UIView:0x2613afd0.width - 293>",
    "<NSAutoresizingMaskLayoutConstraint:0x12ccfd50 h=--& v=-&- H:[UITransitionView:0x12ca7570(768)]>",
    "<NSAutoresizingMaskLayoutConstraint:0xcf18c40 h=-&- v=-&- UIView:0x2613afd0.width == ADTransitionView:0xcf16f20.width - 768>",
    "<NSAutoresizingMaskLayoutConstraint:0xcf19bb0 h=-&- v=-&- ADTransitionView:0xcf16f20.width == UITransitionView:0x12ca7570.width>"
Will attempt to recover by breaking constraint 
<NSAutoresizingMaskLayoutConstraint:0x1946a510 h=-&- v=-&- DetailTableView:0xe39ce00.width == UIView:0x2613afd0.width - 293>
Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

A few notes about the app:

1. I am still a noob when it comes to Auto Layout, so I have been kind of easing into it on some of the less critical areas of the app, but the part of the app in question is still all springs and struts.
2. I am using the ADTransitionView library to do customized view controller transitions.
3. It did not do this until this morning.

If I hit continue a couple of times on the debug console, the app moves along as if there is no problem, so this is not a critical issue, but I still wanted to find out how to take care of this issue first, and then try to figure out what triggered it.

The way that I was able to get around the issue was to look at all of the nib files that make up my view controller, table view, and cells. I found that one of the component nib files was still flagged to use Auto Layout, even though there were no constraints of any kind in that nib file. When I turned off the Auto Layout flag on that file and ran the app, it started to transition between view controllers without the ‘Unable to simultaneously satisfy constraints’ message.

BTW, Happy Birthday to Phil “Scrap Iron” Garner, who was an infielder for the Pittsburgh Pirates in the late 70’s and early 80’s.