Can I use autolayout to provide different constraints for landscape and portrait orientations?

Question

Is it possible to change the constraints when the device is rotated? How might this be achieved?

A simple example might be two images which, in portrait, are stacked

Answer 1

The approach I am using (for better or worse) is to define both sets of constraints (portrait and landscape) in the storyboard editor.

To avoid the storyboard warnings of hell, I place all of one set at a priority of 999, just so it doesn't show red everywhere.

Then I add all of the constraints to outlet collections:

@property (strong, nonatomic) IBOutletCollection(NSLayoutConstraint) NSArray *portraitConstraints;
@property (strong, nonatomic) IBOutletCollection(NSLayoutConstraint) NSArray *landscapeConstraints;

Finally, I implement my ViewControllers's viewWillLayout method:

- (void) viewWillLayoutSubviews {
    [super viewWillLayoutSubviews];
    for (NSLayoutConstraint *constraint in self.portraitConstraints) {
        constraint.active = (UIApplication.sharedApplication.statusBarOrientation == UIDeviceOrientationPortrait);
    }
    for (NSLayoutConstraint *constraint in self.landscapeConstraints) {
        constraint.active = (UIApplication.sharedApplication.statusBarOrientation != UIDeviceOrientationPortrait);
    }
}

This seems to work. I really wish you could set the default active property in the the storyboard editor.