ios - Tap UITabBarItem To Scroll To Top Like Instagram and Twitter -

i'm having issues making feature work , help.

my hierarchy tabbarcontroller -> navigation controller -> tableviewcontroller

what want if on current tab , scrolled down able tap current view's uitabbaritem , scrolled top,like instagram , twitter example.

i have tried many things right here :

older question

but sadly non of answers did job me.

i appreciate manner , thank in advance!

here tableview`controller's code :

import uikit  class barsviewcontroller: uitableviewcontroller,uisearchresultsupdating,uisearchbardelegate,uisearchdisplaydelegate,uitabbarcontrollerdelegate{  //tableview data & non related stuff....  override func scrollviewwillbegindragging(_ scrollview: uiscrollview) {         self.searchcontroller.searchbar.resignfirstresponder()         self.searchcontroller.searchbar.endediting(true)     }   func tabbarcontroller(_ tabbarcontroller: uitabbarcontroller, didselect viewcontroller: uiviewcontroller) {         let tabbarindex = tabbarcontroller.selectedindex         if tabbarindex == 0 {              let indexpath = indexpath(row: 0, section: 0)             let navigvc = viewcontroller as? uinavigationcontroller             let finalvc = navigvc?.viewcontrollers[0] as? barsviewcontroller             finalvc?.tableview.scrolltorow(at: indexpath indexpath, at: .top, animated: true)          }      }  } 

tabbarcontroller.swift code ( code doesn't work ) :

import uikit  class tabbarcontroller: uitabbarcontroller,uitabbarcontrollerdelegate {         override func viewdidload() {     super.viewdidload()      // additional setup after loading view.     self.delegate = self }       override func didreceivememorywarning() {         super.didreceivememorywarning()         // dispose of resources can recreated.     }      func tabbarcontroller(_ tabbarcontroller: uitabbarcontroller, shouldselect viewcontroller: uiviewcontroller) -> bool {         guard let viewcontrollers = viewcontrollers else { return false }         if viewcontroller == viewcontrollers[selectedindex] {             if let nav = viewcontroller as? uinavigationcontroller {                 guard let topcontroller = nav.viewcontrollers.last else { return true }                 if !topcontroller.isscrolledtotop {                     topcontroller.scrolltotop()                     return false                 } else {                     nav.popviewcontroller(animated: true)                 }                 return true             }         }          return true     }  } extension uiviewcontroller {     func scrolltotop() {         func scrolltotop(view: uiview?) {             guard let view = view else { return }              switch view {             case let scrollview uiscrollview:                 if scrollview.scrollstotop == true {                     scrollview.setcontentoffset(cgpoint(x: 0.0, y: -scrollview.contentinset.top), animated: true)                     return                 }             default:                 break             }              subview in view.subviews {                 scrolltotop(view: subview)             }         }          scrolltotop(view: view)     }      var isscrolledtotop: bool {         subview in view.subviews {             if let scrollview = subview as? uiscrollview {                 return (scrollview.contentoffset.y == 0)             }         }         return true     }  } 

here go, should work:

func tabbarcontroller(_ tabbarcontroller: uitabbarcontroller, shouldselect viewcontroller: uiviewcontroller) -> bool {   guard let viewcontrollers = viewcontrollers else { return false }      if viewcontroller == viewcontrollers[selectedindex] {         if let nav = viewcontroller as? zbnavigationcontroller {            guard let topcontroller = nav.viewcontrollers.last else { return true }            if !topcontroller.isscrolledtotop {               topcontroller.scrolltotop()               return false            } else {               nav.popviewcontroller(animated: true)            }            return true         }      }      return true  } 

and then...

extension uiviewcontroller {    func scrolltotop() {     func scrolltotop(view: uiview?) {        guard let view = view else { return }       switch view {      case let scrollview uiscrollview:         if scrollview.scrollstotop == true {            scrollview.setcontentoffset(cgpoint(x: 0.0, y: -scrollview.contentinset.top), animated: true)            return         }      default:         break      }       subview in view.subviews {         scrolltotop(view: subview)      }   }    scrolltotop(view: view)  }   // changed   var isscrolledtotop: bool {   if self uitableviewcontroller {      return (self as! uitableviewcontroller).tableview.contentoffset.y == 0   }   subview in view.subviews {      if let scrollview = subview as? uiscrollview {         return (scrollview.contentoffset.y == 0)      }   }   return true 

}

there's bit in function if uiviewcontroller @ top pop to previous controller