How do I properly resize a UICollectionView so that it fully displays its contents? I have tried many things, including setting its frame, calling ``reloadData`` and invalidating the layout:

    self.collectionView.contentSize = CGSizeMake(300, 2000);
    self.collectionView.frame = CGRectMake(0, 0, 300, 2000);
    [self.collectionView reloadData];
    [self.collectionView.collectionViewLayout invalidateLayout];

but none of this has any effect. After pressing the button I still see the initial view, like this:

![collection view only showing part of the content after frame resize][1]

I have a small demo program where I have a data source producing 100 elements. In Interface Builder I initially set the size of the UICollectionView to a small value so that not all elements fit, after that I press a button after which the code above is executed. I expect the UICollectionView to now show all elements, but it doesn&#39;t.

***EDIT:** The demo program can be found at [https://github.com/mjdemilliano/TestUICollectionView][2].*

***EDIT2:** I have observed that the frame update is lost at some point, because if I press the button again, the current frame is back to the old value. After adding some log statements in the button event handler, the log output is:*

    before: frame = {{0, 58}, {320, 331}}, contentSize = {320, 1190}
    update button pressed
    after: frame = {{0, 0}, {300, 2000}}, contentSize = {300, 2000}
    before: frame = {{0, 58}, {320, 331}}, contentSize = {320, 1190}
    update button pressed
    after: frame = {{0, 0}, {300, 2000}}, contentSize = {300, 2000}

*I don&#39;t understand why the frame change is not kept, what is changing it.*

At some point I will replace the hardcoded values by values obtained from the flow layout, but I wanted to rule that out and keep my example as simple as possible.

Context: What I want to do eventually is the following: I have a scrollable view with various controls like labels and images, and a collection view with dynamic content. I want to scroll all that, not just the collection view, therefore I am not using the collection view&#39;s own scrolling facilities, which work fine.


  [1]: http://i.stack.imgur.com/Wlzkc.png
  [2]: https://github.com/mjdemilliano/TestUICollectionView

UICollectionView autosize height

I have a UIView subclass that draws a circle whose radius changes (with nice bouncy animations). The view is deciding the size of the circle.

I want this UIView subclass to change its frame size to match the animated changes to the circle radius, and I want these changes to modify any NSLayoutConstraints connected to the view (so that views that are constrained to the edge of the circle will move as the circle resizes).

I understand that implementing `-(CGSize)intrinsicContentSize` and calling `invalidateIntrinsicContentSize` when the radius changes will tell constraints to update, but I cant figure out how to animate the changes to `intrinsicContentSize`. 

Calling `invalidateIntrinsicContentSize` from within a [UIView animateWith... block just instantly updates the layout.

Is this even possible, and is there a workaround/better approach?


Animate intrinsicContentSize changes

I have a storyboard with Autolayout and Size Classes. Pretty complicated layout, and unfortunately I can&#39;t really pin down how to reproduce the problem in a new project.  
But the view in question is pinned to the left and right edge of the screen with a constraint that has 750 priority (i.e. `|-(0@750)-[myView]-(0@750)-|`, additionally it *has a greater or equal* than constraint with a priority of 1000 (i.e. `|-(&gt;=0)-[myView]-(&gt;=0)-|`). That is done to limit the width on an iPad, so there is a width constraint of `width &lt;= 600 @1000`, and a *center horizontal in container* constraint as well. On top of that the view has a aspect ratio constraint of 3:1. As I said, rather complicated. 

Interface Builder doesn&#39;t show any problems with the constraints. The Xcode layout preview renders correct for all devices.


When I run the app iOS tells me that it has conflicting constraints. 

	Unable to simultaneously satisfy constraints.
		Probably at least one of the constraints in the following list is one you don&#39;t want. Try this: (1) look at each constraint and try to figure out which you don&#39;t expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you&#39;re seeing NSAutoresizingMaskLayoutConstraints that you don&#39;t understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
	(
	    &quot;&lt;NSLayoutConstraint:0x7fd72853ff80 DMXKit.DipSwitchAssembly:0x7fd72990d0e0.width == 3*DMXKit.DipSwitchAssembly:0x7fd72990d0e0.height&gt;&quot;,
	    &quot;&lt;NSLayoutConstraint:0x7fd728574e50 &#39;_UITemporaryLayoutWidth&#39; H:[DMXKit.DipSwitchAssembly:0x7fd72990d0e0(400)]&gt;&quot;,
	    &quot;&lt;NSLayoutConstraint:0x7fd72856e9c0 V:[DMXKit.DipSwitchAssembly:0x7fd72990d0e0(133)]&gt;&quot;
	)

	Will attempt to recover by breaking constraint 
	&lt;NSLayoutConstraint:0x7ffb19798000 DMXKit.DipSwitchAssembly:0x7ffb1979a000.width == 3*DMXKit.DipSwitchAssembly:0x7ffb1979a000.height&gt;


This is repeated a couple of times, with the exact same (i.e. same pointer) constraints. That is strange as well, looks like the constraint isn&#39;t really broken. When run, the app looks 100% correct. When I look at the app in the Xcode view debugger, the constraint with the address `0x7ffb19798000` is still there, so it was never broken. 


Where does the `_UITemporaryLayoutWidth` constaint comes from? Obviously I didn&#39;t add it. Google doesn&#39;t spit out anything useful about `_UITemporaryLayoutWidth`. Did anyone encounter a problem like this?


What is _UITemporaryLayoutWidth and why does it break my constraints?

I keep getting &#39;Unable to simultaneously satisfy constraints&#39; exceptions (Xcode 5, iOS 7, both device and simulator), where one of the constraints in the list is something like this:

    &quot;&lt;NSLayoutConstraint:0x165b23d0 &#39;UIView-Encapsulated-Layout-Width&#39;
    H:[StoryPlayerCell:0x165affc0(0)]&gt;&quot;

I did not set this constraint myself. It&#39;s also not an `NSAutoresizingMaskLayoutConstraint`.
But where does it come from? And how can I get rid of it?

I have no idea.
And I can&#39;t find anything about `&#39;UIView-Encapsulated-Layout-Width&#39;` in the Apple&#39;s documentation.
Even the Google search returns nothing at all.

Any suggestions?

PS: I&#39;m using this cell in a `UICollectionView` with a custom subclass of `UICollectionViewFlowLayout`. Maybe the `&#39;Encapsulated-Layout&#39;` part has something to do with this?

What is a &#39;UIView-Encapsulated-Layout-Width&#39; constraint?

I know that the auto layout chain consists in basically 3 different process.

 1. updating constraints
 2. layout views (here is where we get calculation of frames)
 3. display

What&#39;s is not totally clear to me is the inner difference between `-setNeedsLayout` and `-setNeedsUpdateConstraints`. From Apple Docs:&lt;br&gt; 

[**setNeedsLayout**][1]


&gt; Call this method on your application’s main thread when you want to
&gt; adjust the layout of a view’s subviews. This method makes a note of
&gt; the request and returns immediately. Because this method does not
&gt; force an immediate update, but instead waits for the next update
&gt; cycle, you can use it to invalidate the layout of multiple views
&gt; before any of those views are updated. This behavior allows you to
&gt; consolidate all of your layout updates to one update cycle, which is
&gt; usually better for performance.
&gt;  &lt;br&gt;

[**setNeedsUpdateConstraints**][2]


&gt; When a property of your custom view changes in a way that would impact
&gt; constraints, you can call this method to indicate that the constraints
&gt; need to be updated at some point in the future. The system will then
&gt; call updateConstraints as part of its normal layout pass. Updating
&gt; constraints all at once just before they are needed ensures that you
&gt; don’t needlessly recalculate constraints when multiple changes are
&gt; made to your view in between layout passes.


When I want to animate a view after modifying a constraint and animate the changes I usually call for instance:

    [UIView animateWithDuration:1.0f delay:0.0f usingSpringWithDamping:0.5f initialSpringVelocity:1 options:UIViewAnimationOptionCurveEaseInOut animations:^{
            [self.modifConstrView setNeedsUpdateConstraints];
            [self.modifConstrView layoutIfNeeded];
        } completion:NULL];

I&#39;ve found out that if I use `-setNeedsLayout` instead of `-setNeedsUpdateConstraints` everything work as expected, but if I change `-layoutIfNeeded` with `-updateConstraintsIfNeeded`, the animation won&#39;t happen.&lt;br&gt;
I&#39;ve tried to make my own conclusion:

 - `-updateConstraintsIfNeeded` only update constraints but doesn&#39;t force the layout to come into the process, thus original frames are still preserved
 - `-setNeedsLayout` calls also `-updateContraints` method

So when is ok to use one instead of the other? and about the layout methods, do I need to call them on the view that has a change in a constraint or on the parent view?


  [1]: https://developer.apple.com/reference/uikit/uiview/1622601-setneedslayout
  [2]: https://developer.apple.com/reference/uikit/uiview/1622450-setneedsupdateconstraints

setNeedsLayout vs. setNeedsUpdateConstraints and layoutIfNeeded vs updateConstraintsIfNeeded

I have a view that is laid out completely using auto layout programmatically. I have a UITextView in the middle of the view with items above and below it. Everything works fine, but I want to be able to expand UITextView as text is added. This should push everything below it down as it expands.

I know how to do this the &quot;springs and struts&quot; way, but is there an auto layout way of doing this? The only way I can think of is by removing and re-adding the constraint every time it needs to grow.

UITextView that expands to text using auto layout

I created two views in one superview, and then added constraints between views:

    _indicatorConstrainWidth = [NSLayoutConstraint constraintWithItem:self.view1 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view2 attribute:NSLayoutAttributeWidth multiplier:1.0f constant:0.0f];
    [_indicatorConstrainWidth setPriority:UILayoutPriorityDefaultLow];
    _indicatorConstrainHeight = [NSLayoutConstraint constraintWithItem:self.view1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self.view2 attribute:NSLayoutAttributeHeight multiplier:1.0f constant:0.0f];
    [_indicatorConstrainHeight setPriority:UILayoutPriorityDefaultLow];
    [self addConstraint:_indicatorConstrainWidth];
    [self addConstraint:_indicatorConstrainHeight];

Now I want to change multiplier property with animation, but I can&#39;t figure out how to change the multipler property. (I found _coefficient in private property in header file NSLayoutConstraint.h, but it private.)

How do I change multipler property? 

My workaround is to remove the old constraint and add the new one with a different value for `multipler`.

Can I change multiplier property for NSLayoutConstraint?

Below is the error message I receive in the debug area. It runs fine and nothing is wrong except that I receive this error. Would this prevent apple accepting the app? How do I fix it?

    2012-07-26 01:58:18.621 Rolo[33597:11303] Unable to simultaneously satisfy constraints.
    	Probably at least one of the constraints in the following list is one you don&#39;t want. Try this: (1) look at each constraint and try to figure out which you don&#39;t expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you&#39;re seeing NSAutoresizingMaskLayoutConstraints that you don&#39;t understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
    (
        &quot;&lt;NSAutoresizingMaskLayoutConstraint:0x887d630 h=--&amp; v=--&amp; V:[UIButtonLabel:0x886ed80(19)]&gt;&quot;,
        &quot;&lt;NSAutoresizingMaskLayoutConstraint:0x887d5f0 h=--&amp; v=--&amp; UIButtonLabel:0x886ed80.midY == + 37.5&gt;&quot;,
        &quot;&lt;NSAutoresizingMaskLayoutConstraint:0x887b4b0 h=--&amp; v=--&amp; V:[UIButtonLabel:0x72bb9b0(19)]&gt;&quot;,
        &quot;&lt;NSAutoresizingMaskLayoutConstraint:0x887b470 h=--&amp; v=--&amp; UIButtonLabel:0x72bb9b0.midY == - 0.5&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0x72bf860 V:[UILabel:0x72bf7c0(17)]&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0x72c2430 UILabel:0x72bfad0.top == UILabel:0x72bf7c0.top&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0x72c2370 UILabel:0x72c0270.top == UILabel:0x72bfad0.top&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0x72c22b0 V:[UILabel:0x72bf7c0]-(NSSpace(8))-[UIButton:0x886efe0]&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0x72c15b0 V:[UILabel:0x72c0270]-(NSSpace(8))-[UIRoundedRectButton:0x72bbc10]&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0x72c1570 UIRoundedRectButton:0x72bbc10.baseline == UIRoundedRectButton:0x7571170.baseline&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0x72c21f0 UIRoundedRectButton:0x7571170.top == UIButton:0x886efe0.top&gt;&quot;
    )
    
    Will attempt to recover by breaking constraint 
    &lt;NSLayoutConstraint:0x72bf860 V:[UILabel:0x72bf7c0(17)]&gt;
    
    Break on objc_exception_throw to catch this in the debugger.
    The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in &lt;UIKit/UIView.h&gt; may also be helpful.



Unable to simultaneously satisfy constraints, will attempt to recover by breaking constraint

I have a `UIView` and I set the constraints using Xcode Interface Builder.

Now I need to update that `UIView` instance&#39;s height constant programmatically. 

There is a function that goes like `myUIView.updateConstraints()`, but I don&#39;t know how to use it.


How to update the constant height constraint of a UIView programmatically?

The question I have is simple but I couldn&#39;t find any information in the documentation.

What happens with layout constraints when a view is removed from the view hierarchy (or moved to another view)?

For example, let&#39;s have container `C` with subviews `A` and `B`. Container `C` holds some constraints. Then we call `[A removeFromSuperview]`. What happens with the constraints for `A`?

What then happens if we add `A` to `C` again?

What happens with constraints when a view is removed

I&#39;ve never worked with **autolayout** constraints before. I have a small new app I&#39;m working on and noticed that the NIB&#39;s views are defaulting to autolayout. So, I figured I&#39;d take the opportunity to work *with* it and try to figure out where Apple is going with this. 

First challenge:

I need to resize an MKMapView and I&#39;d like to animate it to the new position. If I do this the way I&#39;m used to:


	[UIView animateWithDuration:1.2f
		 animations:^{
			 CGRect theFrame = worldView.frame;
			 CGRect newFrame = CGRectMake(theFrame.origin.x, theFrame.origin.y, theFrame.size.width, theFrame.size.height - 170);
			 worldView.frame = newFrame;
	}];

...then the MKMapView will &#39;snap&#39; back to its original height whenever a sibling view gets updated (in my case a UISegmentedControl&#39;s title is being updated `[myUISegmentedControl setTitle:newTitle forSegmentAtIndex:0]`).

So, what I *think* I want to do is change the constraints of the MKMapView from being equal to the parent view&#39;s hight to being relative to the top of the UISegmentedControl that it *was* covering: `V:[MKMapView]-(16)-[UISegmentedControl]`

What I want is for the MKMapView height to shorten so that some controls beneath the map view are revealed. To do so I *think* I need to change the constraint from a fixed full size view to one where the bottom is constrained to the top of a UISegmentedControl...and I&#39;d like it to animate as view shrinks to new size.

How does one go about this?


Edit - **this animation is *not* animating** though the bottom of the view does move up 170 instantly:


		[UIView animateWithDuration:1.2f
			 animations:^{
				 self.nibMapViewConstraint.constant = -170;

		}];

and the `nibMapViewConstraint` is wired up in IB to the bottom Vertical Space constraint.

iOS: How does one animate to new autolayout constraint (height)

I have a UIView in my UIViewController in storyboard which I want to add a constraint on to space that view a distance from the top edge.

Now, when I do the usual by ctrl + drag to the ViewController&#39;s main view I only get option to set it to top layout guide.

This is a problem for me because at one point in the app Im going to move the main view up around 20-50px and what happens then is that view I have will not move... because its not aligned to superview.

How can I manually do this in storyboard or do I have to add it programatically?

Im using xcode 6.

Autolayout: Add constraint to superview and not Top Layout Guide?

I&#39;ve set up multiple sets of constraints in IB, and I&#39;d like to programmatically toggle between them depending on some state. There&#39;s a `constraintsA` outlet collection all of which are marked as installed from IB, and a `constraintsB` outlet collection all of which are uninstalled in IB.

I can programmatically toggle between the two sets like so:

    NSLayoutConstraint.deactivateConstraints(constraintsA)
    NSLayoutConstraint.activateConstraints(constraintsB)

But... I can&#39;t figure out *when* to do that. It seems like I should be able to do that once in `viewDidLoad`, but I can&#39;t get that to work. I&#39;ve tried calling `view.updateConstraints()` and `view.layoutSubviews()` after setting the constraints, but to no avail.

I did find that if I set the constraints in `viewDidLayoutSubviews` everything works as expected. I guess I&#39;d like to know two things...

1. Why am I getting this behavior?
2. Is it possible to activate/deactivate constraints from viewDidLoad?


When can I activate/deactivate layout constraints?

I would like the UICollectionView (The red one) to shrink to the height of the content size in this case UICollectionViewCells(the yellow ones) because there is a lot of empty space. What I tried is to use:

    override func layoutSubviews() {
        super.layoutSubviews()
        if !__CGSizeEqualToSize(bounds.size, self.intrinsicContentSize) {
            self.invalidateIntrinsicContentSize()
        }
    }
    
    override var intrinsicContentSize: CGSize {
        return self.collection.contentSize
    }

but `return self.collection.contentSize` always return (width, 0)
and for this reason it shrinks too much to value of height 30 (The value which I set in the XIB file for the height, although I have constaint &gt;= 30).

[![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/bJZra.png

How to adjust height of UICollectionView to be the height of the content size of the UICollectionView?

I&#39;m trying to figure this out since last week without going any step further. Ok, so I need to apply some **constraints** ***programmatically*** in **Swift** to a `UIView` using this code:

    var new_view:UIView! = UIView(frame: CGRectMake(0, 0, 100, 100));
    new_view.backgroundColor = UIColor.redColor();
    view.addSubview(new_view);
    
    var constX:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0);
    self.view.addConstraint(constX);

    var constY:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0);
    self.view.addConstraint(constY);

    var constW:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Width, multiplier: 1, constant: 0);
    self.view.addConstraint(constW);

    var constH:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Height, multiplier: 1, constant: 0);
    self.view.addConstraint(constH);

But Xcode returns this weird output:


    2014-10-03 09:48:12.657 Test[35088:2454916] Unable to simultaneously satisfy constraints.  Probably at least one of the constraints in the following list is one you don&#39;t want. Try this: (1) look at each constraint and try to figure out which you don&#39;t expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you&#39;re seeing NSAutoresizingMaskLayoutConstraints that you don&#39;t understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
    (
	&quot;&lt;NSLayoutConstraint:0x7fa4ea446830 UIView:0x7fa4ea429290.centerX == UIView:0x7fa4ea4470f0.centerX&gt;&quot;,
	&quot;&lt;NSAutoresizingMaskLayoutConstraint:0x7fa4ea4516c0 h=--&amp; v=--&amp; UIView:0x7fa4ea429290.midX == + 50&gt;&quot;,
	&quot;&lt;NSLayoutConstraint:0x7fa4ea452830 &#39;UIView-Encapsulated-Layout-Width&#39; H:[UIView:0x7fa4ea4470f0(375)]&gt;&quot;,
	&quot;&lt;NSAutoresizingMaskLayoutConstraint:0x7fa4ea446db0 h=-&amp;- v=-&amp;- &#39;UIView-Encapsulated-Layout-Left&#39; H:|-(0)-[UIView:0x7fa4ea4470f0]   (Names: &#39;|&#39;:UIWindow:0x7fa4ea444b20 )&gt;&quot;
    )
     
    Will attempt to recover by breaking constraint &lt;NSLayoutConstraint:0x7fa4ea446830 UIView:0x7fa4ea429290.centerX == UIView:0x7fa4ea4470f0.centerX&gt;

    Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in
    &lt;UIKit/UIView.h&gt; may also be helpful.

    2014-10-03 09:48:12.658 Test[35088:2454916] Unable to simultaneously satisfy constraints.  Probably at least one of the constraints in the following list is one you don&#39;t want. Try this: (1) look at each constraint and try to figure out which you don&#39;t expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you&#39;re seeing NSAutoresizingMaskLayoutConstraints that you don&#39;t understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
    (
	&quot;&lt;NSLayoutConstraint:0x7fa4ea44d160 UIView:0x7fa4ea429290.centerY == UIView:0x7fa4ea4470f0.centerY&gt;&quot;,
	&quot;&lt;NSAutoresizingMaskLayoutConstraint:0x7fa4ea451b30 h=--&amp; v=--&amp; UIView:0x7fa4ea429290.midY == + 50&gt;&quot;,
	&quot;&lt;NSLayoutConstraint:0x7fa4ea44cf00 &#39;UIView-Encapsulated-Layout-Height&#39; V:[UIView:0x7fa4ea4470f0(667)]&gt;&quot;,
	&quot;&lt;NSAutoresizingMaskLayoutConstraint:0x7fa4ea452700 h=-&amp;- v=-&amp;- &#39;UIView-Encapsulated-Layout-Top&#39; V:|-(0)-[UIView:0x7fa4ea4470f0]  (Names: &#39;|&#39;:UIWindow:0x7fa4ea444b20 )&gt;&quot;
    )

    Will attempt to recover by breaking constraint &lt;NSLayoutConstraint:0x7fa4ea44d160 UIView:0x7fa4ea429290.centerY == UIView:0x7fa4ea4470f0.centerY&gt;

    Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in &lt;UIKit/UIView.h&gt; may also be helpful.

Can you help me?
Thanks a lot

How to add constraints programmatically using Swift

I&#39;m using auto layout constraints programmatically to layout my custom UITableView cells and I&#39;m correctly defining the cell sizes in `tableView:heightForRowAtIndexPath:`

It&#39;s working just fine on iOS6 and it does _look_ fine in iOS7 as well 

BUT when I run the app on iOS7, here&#39;s the kind of message I see in the console:

	Break on objc_exception_throw to catch this in the debugger.
	The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in &lt;UIKit/UIView.h&gt; may also be helpful.
	2013-10-02 09:56:44.847 Vente-Exclusive[76306:a0b] Unable to simultaneously satisfy constraints.
		Probably at least one of the constraints in the following list is one you don&#39;t want. Try this: (1) look at each constraint and try to figure out which you don&#39;t expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you&#39;re seeing NSAutoresizingMaskLayoutConstraints that you don&#39;t understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
	(
			&quot;&lt;NSLayoutConstraint:0xac4c5f0 V:|-(15)-[UIImageView:0xac47f50]   (Names: &#39;|&#39;:UITableViewCellContentView:0xd93e850 )&gt;&quot;,
			&quot;&lt;NSLayoutConstraint:0xac43620 V:[UIImageView:0xac47f50(62)]&gt;&quot;,
			&quot;&lt;NSLayoutConstraint:0xac43650 V:[UIImageView:0xac47f50]-(&gt;=0)-[UIView:0xac4d0f0]&gt;&quot;,
			&quot;&lt;NSLayoutConstraint:0xac43680 V:[UIView:0xac4d0f0(1)]&gt;&quot;,
			&quot;&lt;NSLayoutConstraint:0xac436b0 V:[UIView:0xac4d0f0]-(0)-|   (Names: &#39;|&#39;:UITableViewCellContentView:0xd93e850 )&gt;&quot;,
			&quot;&lt;NSAutoresizingMaskLayoutConstraint:0xac6b120 h=--&amp; v=--&amp; V:[UITableViewCellContentView:0xd93e850(44)]&gt;&quot;
	)

	Will attempt to recover by breaking constraint 
	&lt;NSLayoutConstraint:0xac43650 V:[UIImageView:0xac47f50]-(&gt;=0)-[UIView:0xac4d0f0]&gt;

And _indeed_ there&#39;s one of the constraint in that list I don&#39;t want :

    &quot;&lt;NSAutoresizingMaskLayoutConstraint:0xac6b120 h=--&amp; v=--&amp; V:[UITableViewCellContentView:0xd93e850(44)]&gt;&quot;

and I cannot set the `translatesAutoresizingMaskIntoConstraints` property of the `contentView` to NO =&gt; it would mess up the entire cell.

44 is the default cell height but I defined my custom heights in the table view delegate so why does the cell contentView has this constraint? What could cause this? 

In iOS6 it&#39;s not happening and everything looks just fine on both iOS6 and iOS7.

My code is quite big so I won&#39;t post it here but feel free to ask for a pastebin if you need it.

To specify how I&#39;m doing it, on cell intialization:

 - I create all my labels, buttons, etc
 - I set their `translatesAutoresizingMaskIntoConstraints` property to NO
 - I add them as subviews of the `contentView` of the cell 
 - I add the constraints on the `contentView`

I&#39;m also deeply interested in understanding why this happens only on iOS7.

Auto layout constraints issue on iOS7 in UITableViewCell

&gt; **Possible Duplicate:**  
&gt; [presentViewController: crash on iOS 6 (AutoLayout)](https://stackoverflow.com/questions/11198981/presentviewcontroller-crash-on-ios-6-autolayout)  

&lt;!-- End of automatically inserted text --&gt;

I&#39;m getting this error when clicking on a button in my app:


    2012-06-28 21:43:36.860 AppName[2403:707] *** Terminating app due to uncaught exception &#39;NSInvalidUnarchiveOperationException&#39;, reason: &#39;Could not instantiate class named NSLayoutConstraint&#39;
    *** First throw call stack:
    (0x3568788f 0x37a2e259 0x35687789 0x356877ab 0x333a254d 0x333a26bb 0x333a2423 0x33333001 0x332a13c7 0x3317ec59 0x330f4c17 0x330ff267 0x330ff1d5 0x3319e59b 0x3319d367 0x331f86a7 0x8fb11 0x355e13fd 0x330d6e07 0x3319c5e7 0x355e13fd 0x330d6e07 0x330d6dc3 0x330d6da1 0x330d6b11 0x330d7449 0x330d592b 0x330d5319 0x330bb695 0x330baf3b 0x3727a22b 0x3565b523 0x3565b4c5 0x3565a313 0x355dd4a5 0x355dd36d 0x37279439 0x330e9cd5 0x8f6cb 0x8f628)
    terminate called throwing an exception

The error complains on this line of code:

    -(IBAction) goToAbout {
        About *screen = [[ About alloc] initWithNibName:@&quot;About&quot; bundle:nil];
        screen.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
        [self presentModalViewController:screen animated:YES];
    }

The error appears only on my iPhone but not on the simulator...



NSLayoutConstraint  crashes ViewController

I have a UITableViewController that doesn&#39;t display any sections if there is nothing to show. I&#39;ve added a label to indicate to the user that there is nothing to display with this code: 

    label = UILabel(frame: CGRectMake(20, 20, 250, 100))
    label.text = &quot;Nothing to show&quot;
    self.tableView.addSubview(label)

But now, I want it to be centered Horizontally and Vertically. Normally, I would choose the two options highlighted (plus ones for height and width) in the screenshot: 

![enter image description here][1]


  [1]: http://i.stack.imgur.com/I953j.png

I&#39;ve tried the following code to add the constraints but the app crashes with error: 

    label = UILabel(frame: CGRectMake(20, 20, 250, 100))
    label.text = &quot;Nothing to show&quot;
            
    let xConstraint = NSLayoutConstraint(item: label, attribute: .CenterX, relatedBy: .Equal, toItem: self.tableView, attribute: .CenterX, multiplier: 1, constant: 0)
    let yConstraint = NSLayoutConstraint(item: label, attribute: .CenterY, relatedBy: .Equal, toItem: self.tableView, attribute: .CenterY, multiplier: 1, constant: 0)
            
    label.addConstraint(xConstraint)
    label.addConstraint(yConstraint)

error: 

    When added to a view, the constraint&#39;s items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
    2014-12-23 08:17:36.755 [982:227877] *** Assertion failure in -[UILabel _layoutEngine_didAddLayoutConstraint:roundingAdjustment:mutuallyExclusiveConstraints:], /SourceCache/UIKit/UIKit-3318.16.21/NSLayoutConstraint_UIKitAdditions.m:560

The label should always center horizontally and vertically because the app supports rotation of the device. 

What am I doing wrong? How do I add these constraints successfully?

Thanks!

Programmatically Add CenterX/CenterY Constraints

I can&#39;t find a way to create a &#39;square&#39; constraint, meaning &#39;width equals height&#39; in Interface Builder. I guess it&#39;s possible to add such constraint programmatically. Is there something I can do in IB? Maybe I just don&#39;t see it? It seems trivial, yet I can&#39;t find it.

&quot;Width equals height&quot; constraint in Interface Builder

I have used auto layout for my view controllers. I have set the V and H positions in constraints, but I want to know how can I increase my button size when it changes to 5s, 6 and 6 Plus. This is the way I added constraints for the login button:

    NSArray *btncon_V=[NSLayoutConstraint constraintsWithVisualFormat:@&quot;V:[btnLogin(40)]&quot; options:0 metrics:nil views:viewsDictionary];
    [btnLogin addConstraints:btncon_V];
    
    NSArray *btncon_POS_H=[NSLayoutConstraint constraintsWithVisualFormat:@&quot;H:|-100-[btnLogin]-100-|&quot; options:0 metrics:nil views:viewsDictionary];
    [self.view addConstraints:btncon_POS_H];
    
    
    NSArray *btncon_POS_V=[NSLayoutConstraint constraintsWithVisualFormat:@&quot;V:|-70-[Title]-130-[lblFirst]-0-[lblSecond]-20-[textusername]-10-[txtpassword]-10-[btnLogin]&quot; options:0 metrics:nil views:viewsDictionary];
    
    [self.view addConstraints:btncon_POS_V];

But my problem is that while it manages the left and right side gap, it&#39;s getting stretched in iPhone 6 and 6 Plus since the height is fixed. How can I increase the size according to the screen size? I think this might be the aspect ratio, but how can I set the aspect ratio constraint in code?

How can I set aspect ratio constraints programmatically in iOS?

I&#39;ve been looking for a lot of snippets in the net and I still can&#39;t find the answer to my problem. My question is I have a scrollView(SV) and I want to add a button inside scrollView(SV) programmatically with same width and height of its superview which is scrollView(SV) so that when user rotate the device button will have the same frame of scrollView(SV). how to do the NSLayout/NSLayoutConstraint? thanks

Width and Height Equal to its superView using autolayout programmatically?

I have a custom UIView subclass which is being initialized via a nib.

In `-awakeFromNib`, I&#39;m creating a subview and attempting to center it in its superview.

    [self setInteralView: [[UIView alloc] init]];
    [[self internalView] addConstraint: [NSLayoutConstraint constraintWithItem: [self internalView]
                                                                     attribute: NSLayoutAttributeCenterX
                                                                     relatedBy: NSLayoutRelationEqual
                                                                        toItem: self
                                                                     attribute: NSLayoutAttributeCenterX
                                                                    multiplier: 1
                                                                      constant: 0]];

This breaks, and causes the following output:

    2013-08-11 17:58:29.628 MyApp[32414:a0b] The view hierarchy is not prepared for the constraint: &lt;NSLayoutConstraint:0xc1dcc80 UIView:0xc132a40.centerX == MyView:0xc1315a0.centerX&gt;
    	When added to a view, the constraint&#39;s items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
    2013-08-11 17:58:29.630 MyApp[32414:a0b] View hierarchy unprepared for constraint.
    	Constraint: &lt;NSLayoutConstraint:0xc1dcc80 UIView:0xc132a40.centerX == MyView:0xc1315a0.centerX&gt;
    	Container hierarchy: 
    &lt;UIView: 0xc132a40; frame = (0 0; 0 0); clipsToBounds = YES; layer = &lt;CALayer: 0xc132bc0&gt;&gt;
    	View not found in container hierarchy: &lt;MyView: 0xc1315a0; frame = (-128 -118; 576 804); layer = &lt;CALayer: 0xc131710&gt;&gt;
    	That view&#39;s superview: &lt;UIView: 0xc131a70; frame = (0 0; 320 568); autoresize = W+H; layer = &lt;CALayer: 0xc131b50&gt;&gt;

Centering subview&#39;s X in autolayout throws &quot;not prepared for the constraint&quot;

I have gone through and removed every single user constraint yet I am still getting the following error **ONLY** after I rotate the device. I have absolutely no clue why though. Does anyone have any ideas?


    2013-01-14 21:30:31.363 myApp[35869:c07] Unable to simultaneously satisfy constraints.
    	Probably at least one of the constraints in the following list is one you don&#39;t want. Try this: (1) look at each constraint and try to figure out which you don&#39;t expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you&#39;re seeing NSAutoresizingMaskLayoutConstraints that you don&#39;t understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
    (
        &quot;&lt;NSAutoresizingMaskLayoutConstraint:0x84543d0 h=--&amp; v=--&amp; V:[UIView:0xa330270(768)]&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0xa338350 V:[UIView:0xa331260]-(-1)-|   (Names: &#39;|&#39;:UIView:0xa330270 )&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0xa338390 V:|-(841)-[UIView:0xa331260]   (Names: &#39;|&#39;:UIView:0xa330270 )&gt;&quot;
    )
    
    Will attempt to recover by breaking constraint 
    &lt;NSLayoutConstraint:0xa338350 V:[UIView:0xa331260]-(-1)-|   (Names: &#39;|&#39;:UIView:0xa330270 )&gt;
    
    Break on objc_exception_throw to catch this in the debugger.
    The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in &lt;UIKit/UIView.h&gt; may also be helpful.



Unable to simultaneously satisfy constraints - No constraints in place

I want my `UIImageView` to grow or shrink depending on the size of what the actual image it&#39;s displaying is. But I want it to stay vertically centered and 10pts from the leading edge of the superview.

However, if I set these two constraints it complains I haven&#39;t set up enough constraints to satisfy Auto Layout. To me it seems to perfectly describe what I want. What am I missing?

With Auto Layout, how do I make a UIImageView&#39;s size dynamic depending on the image?

I just finished an app on iOS 6 and bought a developer account a week ago so haven&#39;t had much time playing with the iOS 7 SDK. Just downloaded the Golden Master version and trying to upgrade my app to be compatible with iOS 7. 

I received a lot of warnings saying 

&gt; Misplaced View Frame for &quot;Label - Label&quot; will be different at run time.

and I am unable to run the program. The project contains tableview and its is parsing and displaying XML feed from an RSS. 

How to fix this issue?

iOS 7: Misplaced View Frame for &quot;Label - Label&quot; will be different at run time

Apple&#39;s [documentation](https://developer.apple.com/library/ios/documentation/uikit/reference/UIViewController_Class/index.html#//apple_ref/occ/instp/UIViewController/topLayoutGuide) on creating Auto Layout constraints between a view and one of the layout guides only shows an example using [VFL](https://developer.apple.com/library/mac/documentation/userexperience/conceptual/AutolayoutPG/Articles/formatLanguage.html).

Is there any way to create these constraints programmatically **without** VFL (using [`NSLayoutConstraint`&#39;s other API](https://developer.apple.com/library/mac/documentation/AppKit/Reference/NSLayoutConstraint_Class/index.html#//apple_ref/occ/clm/NSLayoutConstraint/constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:) or similar)?

(Note: I&#39;m specifically asking about doing this in code, not in Interface Builder. And I don&#39;t want the calculated `length` of the guide set as a static constant on a constraint, I want a constraint where changes to the layout guide length would automatically cause the constrained view to adjust position.)

Creating Auto Layout constraints to topLayoutGuide and bottomLayoutGuide in code

I&#39;ve read the [documentation](https://developer.apple.com/documentation/uikit/uiview/1622572-translatesautoresizingmaskintoco). But I&#39;m still not sure when I need to not set it to `false`. In the code below if I set it to `false` I won&#39;t see the header at all. If I leave it as `true`, then everything is fine.

The following in  View debug hierarchy will give a warning &quot;**width** and **position** are ambiguous&quot;. 

    func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -&gt; UIView? {
        
        let header = UIView()
        header.translatesAutoresizingMaskIntoConstraints = false
        header.backgroundColor = .orange
        header.heightAnchor.constraint(equalToConstant: 10).isActive = true
            
        return header
    }

I thought whenever I need to modify anything in the code I would have to set `translatesAutoresizingMaskIntoConstraints` to `false`.

Perhaps it&#39;s more correct to say if you need to remove all its constraints then set it to `false` and then add what you like, and in that case you would need to add constraints for all 4 sides.

However, if you need to just keep what the system provides to you, in this case that would be the tableView managing its position and width then leave to `true`.

Is that right?


When should translatesAutoresizingMaskIntoConstraints be set to true?

At the moment, I&#39;m using a `UITableView` along with other views that are contained in a `UIScrollView`. I want the `UITableView` to have its height to be the same as its content height.

To complicate things, I&#39;m also inserting / deleting rows to provide an accordion effect so that when the user taps on a row, it will show more detail for that row.

I&#39;ve got the insert / deletion done, though at the moment it doesn&#39;t update the UIScrollView which is its superview so that the content size of the `UIScrollView` is recalculated and the `UITableView` along with other views in the `UIScrollView` are displayed correctly.

How can I go about implementing this so that `UIScrollView`&#39;s size is adjusted and its contents laid out correctly when I change the content of the `UITableView`? I&#39;m currently using auto layout.

UITableView within UIScrollView using autolayout

I am new in auto layout. I have done all of my project from xib file, but now I faced a problem where I have to update an view&#39;s height programmatically. I have tried below but now working.

    [[self view] addConstraint:[NSLayoutConstraint constraintWithItem:loginContainer attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:loginFrame.size.height]];

In console it&#39;s shows

    Unable to simultaneously satisfy constraints.
    	Probably at least one of the constraints in the following list is one you don&#39;t want. Try this: (1) look at each constraint and try to figure out which you don&#39;t expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you&#39;re seeing NSAutoresizingMaskLayoutConstraints that you don&#39;t understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
    (
        &quot;&lt;NSLayoutConstraint:0x78724530 V:[UIView:0x790cdfb0(170)]&gt;&quot;,
        &quot;&lt;NSLayoutConstraint:0x787da210 V:[UIView:0x790cdfb0(400)]&gt;&quot;
    )
    
    Will attempt to recover by breaking constraint 
    &lt;NSLayoutConstraint:0x78724530 V:[UIView:0x790cdfb0(170)]&gt;
    
    Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
    The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in &lt;UIKit/UIView.h&gt; may also be helpful.

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