title: Does global variable always stays in memory..?
body: <p>Here are some global constants and variables declared, so i want to know that whether thses types of initialized properties always stay in the memory?
  Or are these the computed properties that every time i access them, a new instance is created and is lost as soon as its reference goes out of scope?</p>
  
  <pre><code>let storyboard                      =   UIStoryboard(name: "Main", bundle: nil)
  let APPDELEGATE                     =   UIApplication.sharedApplication().delegate as! AppDelegate
  var mainNavigationController        :   UINavigationController?
  var slideMenuNavigationController   :   UINavigationController?
  let clientIDInstagrm                =   "favf5"
  var selectPhotoCount                =   0
  
  
  //URL
  let BASE_URL_FOR_ALBUM            = "http://admin.com/"
  let BASE_URL                      = "http://admin.com"
  
  
  
  //SIGN UP KEYS
  let kNAME           =   "name"
  let kEMAIL          =   "email"
  let kPASS           =   "password"
  let kAPP_KEY        =   "appkey"
  let kDEVICE_TOKEN   =   "device_token"
  let kDEVICE_TYPE    =   "device_type"
  let kServiceMethod  =   "method"
  let kSocialType     =   "social_type"
  let kSocial_id      =   "social_id"
  let kMethod         =   "method"
  
  //KEYS RESPONSE
  let kERROR_CODE     =   "error_code"
  let kUSER_DETAIL    =   "User_details"
  let kUSERNAME       =   "username"
  let kIS_SELECTED    =   "SELECTED"
  
  //BOOK PAGES KEYS
  let kTEMPLATE_TYPE  =   "templateType"
  let kIMAGE_1        =   "img1"
  let kIMAGE_2        =   "img2"
  let kIMAGE_3        =   "img3"
  let kRightSidePage  =   "RightSidePage"
  </code></pre>