title: Pass variables between controller?
body: <p>I have several view controllers, which needs to use some common variables, It seems that I have several ways to do that</p>
  
  <p>1) Global variable defined in AppDelegate</p>
  
  <p>2) Use Segue to pass objects between</p>
  
  <p>3) Use delegate pattern?</p>
  
  <p>Could you let me know which way is better?</p>