title: how to use addConstraint and NSLayoutConstraint in objective c
body: <p>I have a two horizontal space constraint in storyboard that take the left and right of view in table cell .</p>
  
  <p>storyboard constraint:</p>
  
  <pre><code> Horizontal Space - Content View - View
  </code></pre>
  
  <p>this is the IBOutlet that connect to this constraint</p>
  
  <pre><code> @property (nonatomic, weak) IBOutlet NSLayoutConstraint *contentViewRightConstraint;
   @property (nonatomic, weak) IBOutlet NSLayoutConstraint *contentViewLeftConstraint;
  </code></pre>
  
  <p>Can I do this in code ?</p>
  
  <p>I found this but I don't know how to work with this.</p>
  
  <p>And where I add this code.</p>
  
  <pre><code>[self.view addConstraint:[NSLayoutConstraint 
       constraintWithItem:label
       attribute:NSLayoutAttributeCenterX
       relatedBy:NSLayoutRelationEqual
       toItem:self.view
       attribute:NSLayoutAttributeCenterX
       multiplier:1.0
       constant:0.0]];
  </code></pre>