title: how to change an uilabel from another class
body: <p>I have my ViewController.h/m and another class Keyboard.h/m.
  In my ViewController.h I have an UILabel:</p>
  
  <pre><code>@interface ViewController : UIViewController{
  
  UILabel *label;
  
  }
  
  @property (nonatomic, retain) IBOutlet UILabel *label;
  </code></pre>
  
  <p>and my ViewController.m looks so</p>
  
  <pre><code>#import "ViewController.h"
  @synthesize label;
  ...
  </code></pre>
  
  <p>Now I want to change the label from Keyboard.m. 
  I have tried something like this:</p>
  
  <pre><code>#import "ViewController.h"
  ...
  ViewController *vc;
  vc.label.text = @"text";
  </code></pre>
  
  <p>it compiles without any errors but the label doesn't change</p>