title: Objective C const NSString * vs NSString * const
body: <p>I'm trying to a NSString constant in my .h file to be defined in my .m. I understand that<br>
      <code>extern NSString * const variableName;</code> in the .h and<br>
      <code>NSString * const variableName = @"variableValue";</code> is the way to do this.  Examining c tutorials I see that <code>const</code> is supposed to go before variable definitions.  My question is why is it not declared as <code>extern const NSString * variableName;</code> in the .h and <code>const NSString * variableName = @"variableValue";</code> in the .m.  I know this doesn't work because I encounter compiler warnings which say 'Passing argument 1 of methodName: discards qualifiers from pointer target type'.  What does this mean?</p>