title: textDidChange not called ( NSTextFieldDelegate )
body: <p>Step 1. Add a NSTextField in xib </p>
  
  <p>Step 2. Add NSTextFieldDelegate in .h file,Control-drag NSTextField to File's Owner to set delegate to it</p>
  
  <p>Step 3, In .m file add the method:</p>
  
  <pre><code>- (void)textDidChange:(NSNotification *)notification{
      NSLog(@"textDidChange");
  }
  </code></pre>
  
  <p>but the method textDidChange: not called?</p>
  
  <p>Is any mistake?</p>