title: What is the use of Singleton class in objective-c?
body: <p>I know Singleton class is a class whose only one object can be created at a time. </p>
  
  <p>My questions are:</p>
  
  <p>1.<strong>What is</strong> the use of Singleton class in objective-c?</p>
  
  <p>2.<strong>How to</strong> create and use the created Singleton class?</p>