Enable + Disable Auto-Layout Constraints

Enable + Disable Auto-Layout Constraints

Aha!

Constraints become nil (and thus can't be reactivated), once their active property is set to false. Making them strong references (thanks, Caleb, for clearing up the nomenclature) preserves them so they can be activated and deactivated as desired.

Programmatically disable auto-layout constraint

When developing for iOS 8.0 or later, just use isActive property of NSLayoutConstraint after creating your IBOutlet.

UPDATED

• to have strong reference to the outlet per below suggestion, thank you @rob mayoff.
• to use .isActive instead of .active with Swift 4 per below suggestion, thank you @Mohit Singh.

your cell would have the following outlet:

@IBOutlet var photoBottomConstraint: NSLayoutConstraint!

and you would access the constraint in willDisplayCell like:

myCell.photoBottomConstraint.isActive = false

and when you need it again:

myCell.photoBottomConstraint.isActive = true

Enabling/Disabling NSLayoutConstraints in InterfaceBuilder

Select the constraint you want to disable in storyboard, and Option+Command+4 to show Attributes Inspector, then unselect Installed.

How to turn off or turn on the Autolayout in code

In XIB You can Disable AutoLayout In Interface Builder Document

How to turn on/off auto layout for a single view controller in storyboard

It may look like this "Use Auto Layout" checkbox is for a specific scene, but as you've discovered, it's for the entire "Interface Builder Document" (i.e., the entire storyboard). Thus, if you don't want to use auto layout on a particular scene, you are stuck with a few alternatives:

1. You can either put this other scene in a different storyboard or NIB and transition to and from view controller programmatically. You lose many of the storyboard benefits if you do that (e.g. you cannot just create segues back and forth in IB, but rather have to transition to and from this scene programmatically).

2. You could keep auto layout enabled but then for the one view controller in question, you can programmatically:

   • Remove any constraints that IB may have added (esp in Xcode 6);

   • Adjust the autoresizingMask for your various controls. If you want your autoresizingMask to be honored, you may want to turn on translatesAutoresizingMaskIntoConstraints; and

   • If using Xcode 6, you might want to turn off "Use Size Classes", too, so that you're laying out the scene properly for the target device.

   So, having laid out my label the way I wanted in IB, I could then:

   - (void)viewDidLoad {
       [super viewDidLoad];
   
       [self.view removeConstraints:self.view.constraints];
       [self.label removeConstraints:self.label.constraints];
       self.label.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleBottomMargin;
       self.label.translatesAutoresizingMaskIntoConstraints = YES;
   }
   

   Clearly, what you set the autoresizingMask to is entirely up to you (in this example, I put a label centered on scene, so the above keeps it centered as I go to landscape), but hopefully this illustrates the idea.

Frankly, given that there's nothing you can do with autosizing masks that you can't easily express in auto layout, I'd be inclined to stick with auto layout, and you eliminate the awkwardness of the above approaches.

Disable autolayout constraint error messages in debug console output in Xcode

Did some decompiling and there's actually a way:

for Swift 5

UserDefaults.standard.set(false, forKey: "_UIConstraintBasedLayoutLogUnsatisfiable")

Objective-C

[[NSUserDefaults standardUserDefaults] setValue:@(NO) forKey:@"_UIConstraintBasedLayoutLogUnsatisfiable"];

Now you'll only get notified that "_UIConstraintBasedLayoutLogUnsatisfiable is OFF".

Obligatory reminder for anyone reading this: this should be last resort, for tips on debugging and fixing constraint issues see WWDC's "Mysteries of Auto Layout" sessions: part 1 and part 2.

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