title: How to update constraint whenrotate to landscape
body: <p>I have added a constraints to an <code>UIImageView</code> in this way</p>
  
  <pre><code> //-----------Add constraints to rightoval image-----------------
  
  NSArray *constr_V2=[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-100-[rightOval(210)]|"
                                                            options:0
                                                            metrics:nil views:back];
  
  NSArray *constr_H2 = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-rgtOvalX-[rightOval(65)]|"
                                                              options:NSLayoutFormatDirectionLeadingToTrailing
                                                              metrics:metrices
                                                                views:back];
  
  [self.view addConstraints:constr_V2];
  [self.view addConstraints:constr_H2];
  </code></pre>
  
  <p>This <code>rgtOvalX</code>value I calculated in this way</p>
  
  <pre><code>float rgtX=dm.screenWidth-65;
  </code></pre>
  
  <p>65 is my image view width. Its fine in portrait view. But in landscpe view its still takes X position same as the portrait X position. How can I update the constraint when the phone rotates to landscape mode. Please help me.
  Thanks</p>