title: add days onto string date swift
body: <p>I have a variety of dates in String format, held in a dictionary. I would like to retrieve these dates and add one or two days onto them, depending on other criteria.</p>
  
  <p>Do I need to convert the string dates to NSDate, extract the components (year, month, day), edit the components (adding one or two days) and put the new components back together again in NSDate/String?</p>
  
  <p>For example, I have a string date from my dictionary "26/05/2018" and I want to add one day on, I want to produce a new string "27/05/2018".</p>
  
  <p>Thanks</p>