So I have looked around a quite a bit, and nothing on here seems to explain exactly the correct way of doing this. I have 7 UITextFields within a custom UITableViewCell.
Swift version (Based on Eyal's answer)
class MyViewController: UIViewController, ... , UITextFieldDelegate {
@IBOutlet var activeTextField: UITextField! //doesn't need to connect to the outlet of textfield in storyboard
....
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
....
var cellTextField = self.view.viewWithTag(101) as? UITextField
cellTextField!.delegate = self;
....
}