使用Alamofire下载后等待segue时处理用户交互

My project displays elements in a Table View. When the user clicks a cell, the cell expands to show more info (like the App Store updates tab) and if the user taps that expanded cell, the element referred in the cell is opened in a new page (again, like the App Store). That element however has to be downloaded using an Alamofire request before it can be shown. To speed things up, I'm starting the download the element when the cell expands so when the user decides to open the element, it might already have finished downloading.My project displays elements in a Table View. W