Like the title explained well, I'm looking to check if user exist in parse.com while the user is typing. I came out so far with this code from their documentation but if you have better suggestion
let userName = userNameTextField.text
let query = PFUser.query()
query!.whereKey("Username", equalTo:"%userName%")
let usernames = query!.findObjects()
if usernames != nil { print("existing")} else {print("notexisting")}