ios - Delegate of TextField -

i faced , cannot understand it.

in tutorial watched, instructor press (cntrl + click) delegate option , drag viewcontroller class. then, textfield options become photo. searched lot , found explanation ,but couldn't understand exactly.

explanation : able use uitextfielddelegate methods, viewcontroller class must adopt protocol. however, before using method, have choose delegate option.

i cannot understand option. benefit of ?

so in order use , understand try out these steps:

1 adopt uitextfielddelegate protocol class so

    class myviewcontroller: uiviewcontroller, uitextviewdelegate { 

2 implement callback methods uitextviewdelegate. example:

    //mark: uitextviewdelegate      func textfield(_ textfield: uitextfield, shouldchangecharactersin range: nsrange, replacementstring string: string) -> bool {         print(textfield.text ?? "")         return true     } 

these methods made managing , validating text textview. maybe should read protocols.

or if don't understand why setting delegate form storyboard directly it's because way not have property declared in class. done seamlessly , not have in class:

    @iboutlet weak var mytextfield: uitextfield!      //...     override func viewdidload() {         super.viewdidload()         mytextfield.delegate = self     }