title: Auto Layout UIView on constraint change does not animate iOS 7
body: <p>I'm trying to animate a view from "bottom-up" using AutoLayout. </p>
  
  <p>This works great in iOS 8, however, it doesn't animate in iOS 7.</p>
  
  <p>Here is a code snippet:</p>
  
  <pre><code>@interface ViewController ()
  @property (strong) AViewController *aVC;
  @end
  
  @implementation ViewController
  
  - (void)viewDidLoad
  {
      [super viewDidLoad];
      self.aVC = [[AViewController alloc] init];
      self.aVC.view.translatesAutoresizingMaskIntoConstraints = NO;
      [self.view addSubview:self.aVC.view];
      [self.aVC.view autoPinEdgeToSuperviewEdge:ALEdgeLeft withInset:0];
      [self.aVC.view autoSetDimension:ALDimensionHeight    toSize:100];
      [self.aVC.view autoSetDimension:ALDimensionWidth     toSize:320];
       NSLayoutConstraint *constraint = [self.aVC.view autoPinEdgeToSuperviewEdge:ALEdgeBottom withInset:-100];
       [self.view layoutIfNeeded];
      [UIView animateWithDuration:2 animations:^{
          constraint.constant = -25;
          [self.view layoutIfNeeded];
      }];
  
  }
  </code></pre>
  
  <p>I'm using the great <a href="https://github.com/smileyborg/PureLayout" rel="nofollow">PureLayout</a> category, to add constraints easily.</p>
  
  <p>Attaching <a href="https://github.com/justme1/autoLayout" rel="nofollow">project sample on Github</a> - will work on iOS 8 simulator, and not iOS 7 simulator. </p>
  
  <p>Any suggestions on how to make this work on iOS 7?</p>