Constraint is deactivated by the system

Question

I have a constraint in my view controller that gets deactivated by the system for some reason when the app goes into the background and then coming back to foreground. I haven't been able to pinpoint who's deactivating the constraint. I subclassed NSLayoutConstraint to catch when it's deactivated but the precondition is never triggered. So I'm out of ideas why this is happening and how to prevent it.

@IBOutlet private(set) var testConstraint: TestConstraint!


class TestConstraint: NSLayoutConstraint {
    override var isActive: Bool {
        didSet {
            precondition(isActive, "isActive should not be set to false")
        }
    }
}

As a general rule, constraints to not get *"deactivated by the system for some reason "* ... try putting together a [mre] — DonMag, Nov 08 '21 at 20:30

score 1 · Accepted Answer · answered Nov 09 '21 at 09:46

If the constraint is not installed (deactivated) in interface builder for some reason it will be deactivated by the system.

I haven't found any documentation for this but I found this SO post which led me to test to activate the constraint in interface builder and sure enough it stays active when coming from the background.

Constraint is deactivated by the system

1 Answers1