title: NSString on switch case
body: <p>Instead of using else if like this</p>
  
  <pre><code>            if([screen isEqualToString :@"A"]){
  
                 }
               else if(screen isEqualToString:@"B"){
  
                 }
  </code></pre>
  
  <p>Will it work like this</p>
  
  <pre><code>          switch ([string isEqualToString:screen]){
            case ISA:
            break;
  
            case ISB:
            break;
  
            default:
            break;
         }
  </code></pre>
  
  <p>where ISA and ISB is defined like</p>
  
  <pre><code>       #define ISA [screen isEqualToString:A] and **will it be efficient**
  </code></pre>