ios - navigationController is nil while performing segue? -

i using library called swiftpages. works fine. when perform push segue view controller navigation bar self.navigationcontroller nil ?

how can add navigation bar pushed vc ?

viewcontroller

class coursepagecontroller: uiviewcontroller, uitableviewdatasource, uitableviewdelegate {      @iboutlet weak var chaptertable: uitableview!      @iboutlet weak var coursedesc: uitextview!          var coursename : string!          var chapname : [string] = []         var chapid : [string] = []       override func viewdidload() {         super.viewdidload()            self.title = coursename         self.coursedesc.text = coursedescriptionc         self.coursedesc.setcontentoffset(cgpointzero, animated: true)         hud()         chaptertable.estimatedrowheight = 120         chaptertable.rowheight = uitableviewautomaticdimension         getdata()     }      func hud(){             progress.show(style: mystyle())     }      func getdata(){         alamofire.request(.get, "http://www.wve.com/index.php/capp/get_chapter_by_course_id/\(courseidincontroller)")             .responsejson { (_, _, data, _) in                 let json = json(data!)                 let catcount = json.count                 index in 0...catcount-1 {                     let cname = json[index]["chapter_name"].string                     let cid = json[index]["chapter_id"].string                     self.chapname.append(cname!)                     self.chapid.append(cid!)                 }                 self.chaptertable.reloaddata()                 self.progress.dismiss()         }     }      func numberofsectionsintableview(tableview: uitableview) -> int {         // #warning potentially incomplete method implementation.         // return number of sections.         return 1     }       func tableview(tableview: uitableview, numberofrowsinsection section: int) -> int {         // #warning incomplete method implementation.         // return number of rows in section.         return chapname.count     }        func tableview(tableview: uitableview, cellforrowatindexpath indexpath: nsindexpath) -> uitableviewcell {         let cell : uitableviewcell = self.chaptertable.dequeuereusablecellwithidentifier("chapcell") as! uitableviewcell         cell.textlabel?.text = self.chapname[indexpath.row]          return cell     }           func tableview(tableview: uitableview, didselectrowatindexpath indexpath: nsindexpath) {         //here navigationcontroller nil self.navigationcontroller?.pushviewcontroller(self.storyboard!.instantiateviewcontrollerwithidentifier("lessoncontroller") as! uiviewcontroller, animated: true)     //        performseguewithidentifier("chapsegue", sender: nil)         } 

edit

i have added navigation controller initial vc. course page controller shown swiftpages.

i can't find how being presented. please take @ file. https://github.com/gabrielalva/swiftpages/blob/master/swiftpages/swiftpages.swift

thanks in advance!

did put coursepagecontroller in navigationcontroller? if yes check how presented?

if presented modally won't navigationcontroller reference.

this work if have navcontroller rootviewcontroller

if let navcontroller = uiapplication.sharedapplication().keywindow?.rootviewcontroller as? uinavigationcontroller {             //get nav controller here , try push anotherviewcontroller         }