Show and hide views when using AutoLayout - ios

Question

I have some views where I have to remove a UIView and let all the other views rearrange without this view. I usually do this by creating multiple constraints with different weights, so when I removeFromSuperView all the other constraints with lower weight start working and everything rearranges as I want.
It works perfectly but now I have to show and hide the view but when I removeFromSuperView, that view is gone with all its constraints... I have no idea what to do... I can change width and heights constraints to zero for the view I want to hide... but the problem with this is that then I have to hard code the height in the code and I don't like it...
What's the best way of hiding and showing UIViews? Something like the "Installed" property that you can set in the IB but from the code.

Answer 1

When you remove the view from super view you lose the constraint, you're basically making it available for any object in your view and that way you have to write some methods to add to other views (with programmatically adding constraint) or removing it again.
From my experience to hide view you can use constraint animation or view itself animation and throw it off to left, right, up or down. Also for it to not be available within user interaction you can just disable it with self.view.hidden = true or self.view.userInteractionEnabled = false. use dispatch_async() when you also updating view, apple love people who code standard :).
Hide View itself with animation:
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.view.hidden = true // Or userInteractionEnable = false
UIView.animateWithDuration(1.0, delay: 0, options: UIViewAnimationOptions.CurveEaseOut, animations: {
self.reportView.alpha = 0
}, completion: nil)
})
Hide View with Constraint:
You need to create constraint IBOutlet to use the constant with animation.
self.someView.constant = -205 // Throw it off canaves
UIView.animateWithDuration(1.0, delay: 0, options: UIViewAnimationOptions.CurveEaseOut, animations: {
self.view.layoutIfNeeded()
}, completion: { (finished: Bool)-> Void in
self.someView.hidden = true
})
To make it appear just do the same think in reverse. but don't removeFromSuperView(), unless you trying to attach it to First Responder or something like that.

Answer 2

If targeting iOS 9 and above, you can try UIStackView.
One way we can think of preserving constraints is by creating a category on UIView.
#interface UIView (ConstraintsPreserving)
#property (nonatomic, strong) NSMutableArray * preservedConstraints;
-(void)removeFromSuperViewPreservingConstriants;
-(void)addToSuperViewPreservingConstriants:(UIView *)superView;
#end
#import <objc/runtime.h>
#implementation UIView (ConstraintsPreserving)
#dynamic preservedConstraints;
-(void)setPreservedConstraints:(NSMutableArray *)object {
objc_setAssociatedObject(self, #selector(preservedConstraints), object, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
-(NSMutableArray *)preservedConstraints {
return objc_getAssociatedObject(self, #selector(preservedConstraints));
}
-(void)removeFromSuperViewPreservingConstriants
{
if(!self.superview) return;
self.preservedConstraints = [NSMutableArray new];
[self.preservedConstraints addObjectsFromArray:[self constraints]];
for (NSLayoutConstraint * constraint in self.superview.constraints) {
if([constraint.firstItem isEqual:self] || [constraint.secondItem isEqual:self])
[self.preservedConstraints addObject:constraint];
}
[self removeFromSuperview];
}
-(void)addToSuperViewPreservingConstriants:(UIView *)superView
{
if(self.superview) return;
[superView addSubview:self];
[superView addConstraints:self.preservedConstraints];
self.preservedConstraints = nil;
}
#end
PS: This strongly captures the constraints, there by capturing all the view involved in these constraints.

Answer 3

I am not sure if appropriate to your problem, but what I did a couple of times, was to make sure that the view you want to hide is in a container. Such container should have a height and width constraint (and this is where you might not like it). You then create IBOutlets for each one of these constraints in the relevant view controller (control drag from the constraint within storyboard). Finally you can save the initial value of the constraint in viedidload, use it later to switch from zero to that value, whatever it is.

Answer 4

So, I ended up creating creating IBOutlets to the views I want to hide. I set the width and height constraints to zero that way I hide the view. Also I set multiple IBOutlets and changed the priority of this constraints so I can re arrange stuff...
That's the best way I found of doing it.