title: Defining constant for screen width
body: <p>I have a constant defined with screen width to 320. This is being used at multiple places in my code. I have to change this to take value from current device and I do not want to touch all these places. So, I want to define a constant for this with value:</p>
  
  <pre><code>[[UIScreen mainScreen] bounds].size.width
  
  #define kScreenWidth [[UIScreen mainScreen] bounds].size.width
  </code></pre>
  
  <p>But it is giving me lot of compilation errors. Any clue?</p>