title: With autolayout, label position is reset when I change label text
body: <p>I am developing a very simple application in Objective-c.<br>
  In the app, the user can change a position of the label by dragging the screen.</p>
  
  <p>Tap &amp; drag the screen, the label moves up and down to match the position of the finger.<br>
  When you release your finger, the coordinates information of the label is set to its text.</p>
  
  <p>But the label position is reset at the moment its text is changed.</p>
  
  <pre><code>// IBOutlet UILabel *label
  
  - (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
  {
      CGPoint touch = [[touches anyObject] locationInView:self.view];
      label.center = CGPointMake(label.center.x, touch.y);
  }
  
  - (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
  {
      CGPoint touch = [[touches anyObject] locationInView:self.view];
      label.center = CGPointMake(label.center.x, touch.y);
  }
  
  - (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
  {
      CGPoint touch = [[touches anyObject] locationInView:self.view];
      label.text = [NSString stringWithFormat:@"y = %f", touch.y];
  }
  </code></pre>
  
  <p>In <strong>touchesEnded</strong> event, just only change the text of the label,<br>
  but the position of it has reset.</p>
  
  <p>I tried to change <strong>touchesEnded</strong> event like following but it haven't solved the problem.</p>
  
  <pre><code>- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
  {
      CGPoint touch = [[touches anyObject] locationInView:self.view];
      label.text = [NSString stringWithFormat:@"y = %f", touch.y];
      label.center = CGPointMake(label.center.x, touch.y);    // add this line
  }
  </code></pre>
  
  <p>I want to resolve this weird behavior <strong>without uncheck "Use auto layout"</strong>.<br>
  I'd like to keep using auto layout.</p>
  
  <p>I have 4 screenshots for my app.</p>
  
  <p><a href="https://imgur.com/r62ZnVv,CGI0wEr,wwMx7NH,qhcflmv" rel="nofollow noreferrer">4 Screenshots</a></p>
  
  <ol>
  <li>The first image is a Storyboard.<br>
  I have a label with auto layout constraints.</li>
  <li>The second image is a screenshot right after launching app.</li>
  <li>The third image is when a user drag the screen,<br>
  and the label move down to match the finger.</li>
  <li>The forth image is right after release your finger<br>
  and the label text has changed.</li>
  </ol>