title: UIBarButtonSystemItemFlexibleSpace doesn't work in iOS 11
body: <p>In iOS 11 the <code>UIBarButtonSystemItemFlexibleSpace</code> bar button system item type doesn't create any spacing. I was using it to distribute space evenly between bar button items. Is this desired behavior in iOS 11 or a bug? Is there a workaround?</p>
  
  <p>There aren't any notes about any changes for <code>UIBarButtonSystemItemFlexibleSpace</code> in iOS 11 in the current documentation.
  <a href="https://developer.apple.com/documentation/uikit/uibarbuttonsystemitem/uibarbuttonsystemitemflexiblespace" rel="nofollow noreferrer">https://developer.apple.com/documentation/uikit/uibarbuttonsystemitem/uibarbuttonsystemitemflexiblespace</a></p>
  
  <p>Here is an example that in iOS 10 will show three bar button items that are evenly spaced across the entire width of the navigation item.</p>
  
  <pre><code>UIBarButtonItem *flex = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];
  NSArray *items = @[leftButton, flex, middleButton, flex, rightButton];
  [self.navigationItem setLeftBarButtonItems:items animated:YES];
  </code></pre>