iOS

Pitfall: NSLayoutConstraint Breaking in UICollectionView

I encountered a weird error when using UICollectionView, where the storyboard is using autolayout.

This is the error:

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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:0x7fda6411de70 H:[UIButton:0x7fda6411dc90(13)]>",
    ...
    "<NSAutoresizingMaskLayoutConstraint:0x7fda61cf61e0 h=--& v=--& H:[UIView:0x7fda6411d500(50)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fda6411de70 H:[UIButton:0x7fda6411dc90(13)]>

It doesn’t crash as it is able to recover by breaking constraint.

It is weird becase:

  • If I try to solve by breaking the constraint, it will not layout as I wanted

  • I checked every constraints and they are valid and minimal; I need not remove any unwanted constraints

Solution

The problem lies with the view cell.

Somehow, the contentView must set translatesAutoresizingMaskIntoConstraints to NO.

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[cell.contentView setTranslatesAutoresizingMaskIntoConstraints:NO];

This will similarly apply to UITableViewCell.

It seems like the content view cell must use auto resizing mask.

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