iOS 7: Resize the bottom constraint on a view when the keyboard displays. Don't copy-paste directly: the property needs to go in the interface, and be connected to the constraint from IB.

gistfile1.m

// Based on http://stackoverflow.com/a/12925659/2185

@property (strong, nonatomic) IBOutlet NSLayoutConstraint *bottomConstraint;


- (void)viewDidLoad {
  [super viewDidLoad];

  // Subscribe to the keyboard will show notification
  [[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector(keyboardWillShow:)
                                               name:UIKeyboardWillShowNotification object:nil];

  [[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector(keyboardWillHide:)
                                               name:UIKeyboardWillHideNotification object:nil];
}

- (void)keyboardWillShow:(NSNotification *)notification {
  NSDictionary *info = [notification userInfo];
  NSValue *kbFrame = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
  
  // Get the height of keyboard + inputAccessoryView, if there is one
  CGFloat keyboardHeight = CGRectGetHeight([kbFrame CGRectValue]);

  // Adjust the size of the constraint
  self.bottomConstraint.constant += keyboardHeight;
  
  [self.view setNeedsUpdateConstraints];

  NSTimeInterval animationDuration = [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
  [UIView animateWithDuration:animationDuration animations:^{
    [self.view layoutIfNeeded];
  }];
}

- (void)keyboardWillHide:(NSNotification *)notification {
  NSDictionary *info = [notification userInfo];
  NSValue *kbFrame = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
  CGFloat keyboardHeight = CGRectGetHeight([kbFrame CGRectValue]);

  // Adjust the size of the constraint
  self.bottomConstraint.constant -= keyboardHeight;
  [self.view setNeedsUpdateConstraints];

  NSTimeInterval animationDuration = [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
  [UIView animateWithDuration:animationDuration animations:^{
    [self.view layoutIfNeeded];
  }];
}

keyboardWillShow: and keyboardWillHide: could be refactored into a common method.