我如何从已经创建的单元的firebase中拔出密钥

How would I pull the key from firebase of an already created cell (I'm using TableView) that someone tapped on, and create that as a local var? I want to know this so I can transfer the key into the next view so I can make a generic storyboard but the text fields change with the key. This also means I want to set the data in one view controller then send it to another which if I'm using the same database (I am) for this I would need it to be edited on the second view controller. How would I pull the key from firebase of an al