Auto-layout: What creates constraints named UIView

Question

My layout constraints are fine in Interface Builder but an exception occurs at runtime thanks to some part of the framework applying fixed height and width constraints that I really don't want. Why are they there, and how to turn them off?

They're the last two constraints shown in the logged list:

2014-04-26 09:02:58.687 BBCNews[32058:60b] 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) 
(
    "<NSLayoutConstraint:0xbf478a0 UIView:0xbf4a3c0.height == 0.28125*UIView:0xbf4a3c0.width>",
    "<NSLayoutConstraint:0xbf47190 UIView:0xbf4a3c0.leading == BNMyNewsCell_landscape:0xbf48b10.leading>",
    "<NSLayoutConstraint:0xbf47160 UIView:0xbf4a3c0.trailing == BNMyNewsCell_landscape:0xbf48b10.trailing>",
    "<NSLayoutConstraint:0xbf47130 BNMyNewsCell_landscape:0xbf48b10.bottom == UIView:0xbf4a3c0.bottom>",
    "<NSLayoutConstraint:0xbf47100 UIView:0xbf4a3c0.top == BNMyNewsCell_landscape:0xbf48b10.top>",
    "<NSLayoutConstraint:0xd4c3c40 'UIView-Encapsulated-Layout-Width' H:[BNMyNewsCell_landscape:0xbf48b10(304)]>",
    "<NSLayoutConstraint:0xd4c38a0 'UIView-Encapsulated-Layout-Height' V:[BNMyNewsCell_landscape:0xbf48b10(290)]>"
}
Will attempt to recover by breaking constraint 

<NSLayoutConstraint:0xbf478a0 UIView:0xbf4a3c0.height == 0.28125*UIView:0xbf4a3c0.width>

Answer 1

This may not answer your question, but it could help others like me who got here from search.

I was getting a strange AutoLayout broken constraint error accompanied by a UIView-Encapsulated-Layout-Width constraint because I was adding a tableHeaderView to a table view that hadn't been sized with AutoLayout yet. So the system was trying to apply my header subviews' constraints inside a tableview with a frame of {0,0,0,0}. Since UITableView likes control over the width of its elements, its generated width constraint, UIView-Encapsulated-Layout-Width, was set to zero, causing all kinds of confusion with my header elements that were expecting 320+pt width.

The takeaway: make sure you are adding/manipulating your supplementary/header/footer views after the tableview has been sized by AutoLayout.

Answer 2

I catch this problem when I use AL create tableviewHeader

I init tableview like below

let table = UITableView.init(frame: .zero, style: .grouped)
// set table constraint ...

then I create tableviewHeader with AutoLayout.

"<NSLayoutConstraint:0x600003d7d130 'UIView-Encapsulated-Layout-Width' UIView:0x7fe92bc55260.width == 0 (active)>"

symbolic breakpoint appear

After I refer @Yerk 's the answer. I change the frame when I init tableView

let rect = CGRect(x: 0, y: 0, width: SCREEN_WIDTH, height: 0)
let table = UITableView.init(frame:rect , style: .grouped)

The problem seems to be solved

Answer 3

I was having a similar problem found from testing Split View on the iPad Pro, and DesignatedNerd's answer worked but I didn't need so much code. Here is what I used:

[self.tableView.tableHeaderView setTranslatesAutoresizingMaskIntoConstraints:NO];

NSLayoutConstraint *widthConstraint = [NSLayoutConstraint constraintWithItem:self.myTableHeaderView
                                                                   attribute:NSLayoutAttributeWidth
                                                                   relatedBy:NSLayoutRelationEqual
                                                                      toItem:self.tableView
                                                                   attribute:NSLayoutAttributeWidth
                                                                  multiplier:1
                                                                    constant:0];
NSLayoutConstraint *yConstraint = [NSLayoutConstraint constraintWithItem:self.myTableHeaderView
                                                               attribute:NSLayoutAttributeTop
                                                               relatedBy:NSLayoutRelationEqual
                                                                  toItem:self.tableView
                                                               attribute:NSLayoutAttributeTop
                                                              multiplier:1
                                                                constant:0];


[self.tableView addConstraints:@[widthConstraint, yConstraint]];

Note the addition of the Y Constraint, which binds the top of the tableHeaderView to the top of the tableView.

Answer 4

I was facing the same weird constraint and had no idea why, until I remembered the darned translatesAutoresizingMaskIntoConstraints property. Setting this to false solved the problem. What happens in the background is that the auto resizing masks (the old layout engine for iOS) are converted to constraints. Very often you don't want these constraints and want your own ones. In such cases you should set this property to false and you'll be fine:

view.translatesAutoresizingMaskIntoConstraints = false

Answer 5

I got this error in all sorts of circumstances (not necessarily tied to UICollectionView and friends as suggested by the correct answer here)..

So my way of dealing with it was simply clearing all the constraints then building them again (only this time i have no fear of my constraints colliding with these pre-created ones):

so in code:

UIView *parentView = [viewInQuestion superview];
[parentView clearConstraintsOfSubview:viewInQuestion];

where clearConstraintsOfSubview is a category method on UIView:

- (void)clearConstraintsOfSubview:(UIView *)subview
{
    for (NSLayoutConstraint *constraint in [self constraints]) {
        if ([[constraint firstItem] isEqual:subview] || [[constraint secondItem] isEqual:subview]) {
            [self removeConstraint:constraint];
        }
    }
}

Answer 6

I had the same issue when adding constraints to a Table view header. It seem to occur when adding constraints with set constants when the bounds of the header was (0,0,0,0). I managed to fix this by only adding the constraints in the layout subviews method when the bounds of the header was not (0,0,0,0)

    if self.bounds == CGRect.zero {
        return
    }