ios - How do I cut off the text view after 20 characters? -

i trying limit number of characters inside text view 20. after 20 should instead have "...". function not firing , setting delegate correctly.

animal class

cell.pn.text = np[indexpath.row] cell.pn.selectable = false cell.pn.delegate = self 

extension of animal class

extension animal : uitextviewdelegate{ func textview(textview: uitextview, shouldchangetextinrange range: nsrange, replacementtext text: string) -> bool {     return textview.text.characters.count + (text.characters.count - range.length) <= 20     } } 

you can use this:

            if displayname.characters.count > 20 {                 displayname = (displayname nsstring).substringtoindex(20)                 displayname.appendcontentsof("...")             }