title: Connecting next field chain for form text fields
body: <p>I'm trying to connect the text fields in a sign up form so that, upon done being pressed for each, the next field in the form automatically becomes active. To achieve this, I've extended the UITextField class, as follows, in the view controller for the sign up view. </p>
  
  <pre><code>@interface UITextField (Extended)
      @property (nonatomic, weak) IBOutlet UITextField* nextField;
  @end
  </code></pre>
  
  <p>I've then set the nextField outlets via interface builder for each field in the form, and have the following code implemented in the view controller, which is also acting as the delegate for the text fields in the form.</p>
  
  <pre><code>- (BOOL) textFieldShouldReturn:(UITextField *)textField {
      [textField resignFirstResponder];
      UITextField* field = textField.nextField;
      if (field)
          [field becomeFirstResponder];
      return NO;
  }
  </code></pre>
  
  <p>However when building and running the app, it immediately crashes giving the following error : </p>
  
  <pre><code>*** Terminating app due to uncaught exception 'NSUnknownKeyException', 
  reason:'[&lt;UITextField 0x78729580&gt; setValue:forUndefinedKey:]: 
  this class is not key value coding-compliant for the key nextField.'
  </code></pre>
  
  <p>A bit lost as to how to address this, any help would be appreciated! Thanks in advance.</p>