title: stop dispatch_time_t when a button is clicked
body: <p>i am implementing a simple dispatch timer to execute a few lines of code after two minutes of invocation of the timer. the code is as follows,</p>
  
  <pre><code>dispatch_time_t poptime = dispatch_time (DISPATCH_TIME_NOW, delayInSeconds *NSEC_PER_SEC);
  dispatch_after(poptime,dispatch_get_main_queue(), ^(void){
  
                //some code here
  });
  </code></pre>
  
  <p>what i am looking for is to either kill or stop or modify the timer to infinity when a button is clicked. i have the button click function and this dispatch timer is written in viewdidload function of class.</p>
  
  <p>Is this possible? please help 
  thanks.</p>