ios - Index out of bounds error for UIView animation method -

i getting index out of bounds error, can't figure out why. code compiles fine, error appears @ following line (animation):

import uikit  class menuviewcontroller: uiviewcontroller {      private let contentview = uiview()     private let logoview = uiimageview()     private let buttonview = uiview()     private var gamebuttons = [roundedbutton]()     private let scoreview = uiview()     private let titlelabel = uilabel()     private let recentscorelabel = uilabel()     private let highscorelabel = uilabel()      private let titles = [         "multiple choice",         "image quiz",         "right or wrong",         "emoji riddle"      ]      private var recentscores = [int]()     private var highscores = [int]()     private var scoreindex = 0     private var timer = timer()      private var midxconstraints: [nslayoutconstraint]!     private var leftconstraints: [nslayoutconstraint]!     private var rightconstraints: [nslayoutconstraint]!      override  func viewdidload() {         super.viewdidload()         navigationcontroller?.navigationbar.barstyle = .blacktranslucent         navigationcontroller?.navigationbar.tintcolor = uicolor.white         view.backgroundcolor = uicolor(red: 41/255, green: 128/255, blue: 185/255, alpha: 1.0)         layoutview()     }      override func viewwillappear(_ animated: bool) {         navigationcontroller?.navigationbar.ishidden = true     }      func updatescores() {         recentscores = [             userdefaults.standard.integer(forkey: multiplechoicerecentscoreidentifier),             userdefaults.standard.integer(forkey: imagequizrecentscoreidentifier),             userdefaults.standard.integer(forkey: rightwrongrecentscoreidentifier),             userdefaults.standard.integer(forkey: emojirecentscoreidentifier)         ]          highscores = [             userdefaults.standard.integer(forkey: multiplechoicehighscoreidentifier),             userdefaults.standard.integer(forkey: imagequizhighscoreidentifier),             userdefaults.standard.integer(forkey: rightwronghighscoreidentifier),             userdefaults.standard.integer(forkey: emojihighscoreidentifier)         ]     }      func layoutview() {         contentview.translatesautoresizingmaskintoconstraints = false         view.addsubview(contentview)          logoview.translatesautoresizingmaskintoconstraints = false         contentview.addsubview(logoview)         logoview.image = uiimage(named: "logo")          buttonview.translatesautoresizingmaskintoconstraints = false         contentview.addsubview(buttonview)          (index,title) in titles.enumerated() {             let button = roundedbutton()             button.translatesautoresizingmaskintoconstraints = false             buttonview.addsubview(button)             button.backgroundcolor = uicolor(red: 52/255, green: 152/255, blue: 219/255, alpha: 1.0)             button.titlelabel?.font = uifont.boldsystemfont(ofsize: 20)             button.settitle(title, for: .normal)             button.tag = index             gamebuttons.append(button)         }          scoreview.translatesautoresizingmaskintoconstraints = false         contentview.addsubview(scoreview)          titlelabel.translatesautoresizingmaskintoconstraints = false         recentscorelabel.translatesautoresizingmaskintoconstraints = false         highscorelabel.translatesautoresizingmaskintoconstraints = false         scoreview.addsubview(titlelabel)         scoreview.addsubview(recentscorelabel)         scoreview.addsubview(highscorelabel)          titlelabel.textalignment = .center         titlelabel.font = uifont.boldsystemfont(ofsize: 30)         titlelabel.textcolor = uicolor.white         recentscorelabel.textcolor = uicolor.white         highscorelabel.font = uifont.boldsystemfont(ofsize: 20)         highscorelabel.textcolor = uicolor.white          titlelabel.text = titles[scoreindex]         recentscorelabel.text = "recent: " + string(userdefaults.standard.integer(forkey: multiplechoicerecentscoreidentifier))         highscorelabel.text = "highscore: " + string(userdefaults.standard.integer(forkey: multiplechoicehighscoreidentifier))          let constraints = [             contentview.topanchor.constraint(equalto: toplayoutguide.bottomanchor, constant: 8.0),             contentview.leadinganchor.constraint(equalto: view.leadinganchor),             contentview.trailinganchor.constraint(equalto: view.trailinganchor),             contentview.bottomanchor.constraint(equalto: view.bottomanchor),             logoview.topanchor.constraint(equalto: contentview.topanchor, constant: 20.0),             logoview.widthanchor.constraint(equalto: contentview.widthanchor, multiplier: 0.6),             logoview.centerxanchor.constraint(equalto: contentview.centerxanchor),             logoview.heightanchor.constraint(equalto: contentview.heightanchor, multiplier: 0.2),             buttonview.topanchor.constraint(equalto: logoview.bottomanchor, constant: 20.0),             buttonview.bottomanchor.constraint(equalto: scoreview.topanchor, constant: -20.0),             buttonview.widthanchor.constraint(equalto: contentview.widthanchor, multiplier: 0.6),             buttonview.centerxanchor.constraint(equalto: contentview.centerxanchor),             gamebuttons[0].topanchor.constraint(equalto: buttonview.topanchor, constant: 8.0),             gamebuttons[0].bottomanchor.constraint(equalto: gamebuttons[1].topanchor, constant: -8.0),             gamebuttons[0].leadinganchor.constraint(equalto: buttonview.leadinganchor),             gamebuttons[0].trailinganchor.constraint(equalto: buttonview.trailinganchor),             gamebuttons[1].bottomanchor.constraint(equalto: gamebuttons[2].topanchor, constant: -8.0),             gamebuttons[1].leadinganchor.constraint(equalto: buttonview.leadinganchor),             gamebuttons[1].trailinganchor.constraint(equalto: buttonview.trailinganchor),             gamebuttons[2].bottomanchor.constraint(equalto: gamebuttons[3].topanchor, constant: -8.0),             gamebuttons[2].leadinganchor.constraint(equalto: buttonview.leadinganchor),             gamebuttons[2].trailinganchor.constraint(equalto: buttonview.trailinganchor),             gamebuttons[3].bottomanchor.constraint(equalto: buttonview.bottomanchor, constant: -8.0),             gamebuttons[3].leadinganchor.constraint(equalto: buttonview.leadinganchor),             gamebuttons[3].trailinganchor.constraint(equalto: buttonview.trailinganchor),             gamebuttons[0].heightanchor.constraint(equalto: gamebuttons[1].heightanchor),             gamebuttons[1].heightanchor.constraint(equalto: gamebuttons[2].heightanchor),             gamebuttons[2].heightanchor.constraint(equalto: gamebuttons[3].heightanchor),             scoreview.bottomanchor.constraint(equalto: contentview.bottomanchor, constant: -40.0),             scoreview.widthanchor.constraint(equalto: contentview.widthanchor, multiplier: 0.6),             scoreview.heightanchor.constraint(equalto: contentview.heightanchor, multiplier: 0.3),             titlelabel.topanchor.constraint(equalto: scoreview.topanchor, constant: 8.0),             titlelabel.leadinganchor.constraint(equalto: scoreview.leadinganchor),             titlelabel.trailinganchor.constraint(equalto: scoreview.trailinganchor),             titlelabel.bottomanchor.constraint(equalto: recentscorelabel.topanchor, constant: -8.0),             recentscorelabel.leadinganchor.constraint(equalto: scoreview.leadinganchor),             recentscorelabel.trailinganchor.constraint(equalto: scoreview.trailinganchor),             recentscorelabel.bottomanchor.constraint(equalto: highscorelabel.topanchor, constant: -8.0),             highscorelabel.leadinganchor.constraint(equalto: scoreview.leadinganchor),             highscorelabel.trailinganchor.constraint(equalto: scoreview.trailinganchor),             highscorelabel.bottomanchor.constraint(equalto: scoreview.bottomanchor, constant: -8.0),             titlelabel.heightanchor.constraint(equalto: recentscorelabel.heightanchor),             recentscorelabel.heightanchor.constraint(equalto: highscorelabel.heightanchor)         ]          midxconstraints = [scoreview.centerxanchor.constraint(equalto: contentview.centerxanchor)]         leftconstraints = [scoreview.trailinganchor.constraint(equalto: contentview.leadinganchor)]         rightconstraints = [scoreview.leadinganchor.constraint(equalto: contentview.trailinganchor)]          nslayoutconstraint.activate(constraints)         nslayoutconstraint.activate(midxconstraints)          timer = timer.scheduledtimer(timeinterval: 3.0, target: self, selector: #selector(nextscores), userinfo: nil, repeats: true)     }      func nextscores() {         scoreindex = scoreindex < (recentscores.count - 1) ? scoreindex + 1 : 0         uiview.animate(withduration: 1.0, animations: {             nslayoutconstraint.deactivate(self.midxconstraints)             nslayoutconstraint.activate(self.leftconstraints)             self.view.layoutifneeded()         }) {(completion: bool) in             self.titlelabel.text = self.titles[self.scoreindex]             self.recentscorelabel.text  = "recent: " + string(self.recentscores[self.scoreindex]) //index out of bounds error appears here             self.highscorelabel.text = "highscore: " + string(self.highscores[self.scoreindex])             nslayoutconstraint.deactivate(self.leftconstraints)             nslayoutconstraint.activate(self.rightconstraints)             self.view.layoutifneeded()             uiview.animate(withduration: 1.0, animations: {                 nslayoutconstraint.deactivate(self.rightconstraints)                 nslayoutconstraint.activate(self.midxconstraints)                 self.view.layoutifneeded()             })         }     }    } 

the recentscores empty array, i.e. has 0 elements, , trying access first element. don't append element array. that's why "index out of bounds" error.

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