title: Which is the best way to suppress "unused variable" warning
body: <p>There are 3 (which I know) ways to suppress the  "unused variable" warning. Any particular way is better than other ?</p>
  
  <p>First </p>
  
  <pre><code>- (void)testString:(NSString *)testString
  {
       (void)testString;
  }
  </code></pre>
  
  <p>Second</p>
  
  <pre><code>- (void)testString:(NSString *)__unused testString
  {
  
  }
  </code></pre>
  
  <p>Third</p>
  
  <pre><code>- (void)testString:(NSString *)testString
  {
      #pragma unused(testString)
  }
  </code></pre>