title: Static string variable in Objective C on iphone
body: <p>How to create &amp; access static string in iPhone (objective c)? 
  I declare <code>static NSString *str = @"OldValue"</code> in class A.</p>
  
  <p>If i assign some value to this in class B as <code>str = @"NewValue"</code>.
  This value persists for all methods in class B. But if I access it in class C (after assignment in B) I am getting it as OldValue.
  Am I missing something? Should i use extern in other classes?</p>
  
  <p>Thanks &amp; Regards,
  Yogini</p>