ios - Swift Array Resetting Itself -

i have 2 arrays: pointhistory , datehistory. have nstimer, , when timer runs out, action called. in action appending int pointhistory, , current date string datehistory. here timer action:

 func timeraction() {     let steppervalue = int(stepper.value)     employee.numberofpoints = steppervalue      networking.saveemployee(employee, completion: { (error) -> void in         if error != nil {             let alert = uialertcontroller(title: "error", message: "there error updating \(self.employee.name)'s points", preferredstyle: .alert)             let alertaction = uialertaction(title: "ok", style: .cancel, handler: nil)             alert.addaction(alertaction)             self.presentviewcontroller(alert, animated: true, completion: nil)         }     })      var dateformatter = nsdateformatter()     dateformatter.dateformat = "mm-dd-yyyy"     dateformatter.timezone = nstimezone.localtimezone()      var date = nsdate()     var datestring = dateformatter.stringfromdate(date)      //appending here     self.pointhistory.append(self.employee.numberofpoints)     self.datehistory.append(datestring) } 

however, when view loads up, these 2 arrays reset being empty. here viewdidload method:

override func viewdidload() {     super.viewdidload()      self.view.backgroundcolor = uicolor.whitecolor()     self.title = employee.name       editbarbuttonitem = uibarbuttonitem(barbuttonsystemitem: uibarbuttonsystemitem.edit, target: self, action: selector("edit"))     if let font = uifont(name: "avenir", size: 18) {         editbarbuttonitem.settitletextattributes([nsfontattributename: font], forstate: uicontrolstate.normal)     }     self.navigationitem.rightbarbuttonitem = editbarbuttonitem      if let font = uifont(name: "avenir", size: 17) {         uibarbuttonitem.appearance().settitletextattributes([nsfontattributename: font], forstate: uicontrolstate.normal)     }      self.addscrollview()     self.addprofilepicture()     self.adduielements()     self.addlinechart()      setchart(datehistory, yvals: pointhistory)  } 

the whole point of datehistory , pointhistory me add line chart app, , of data stored in these arrays. lao why see setchart function. linechart, using ios charts framework. here actual body of setchart function, called in viewdidload:

 func setchart(xvals: [string], yvals: [int]) {     var dataentries = [chartdataentry]()      in 0..<xvals.count {         let dataentry = chartdataentry(value: double(yvals[i]), xindex: i)         dataentries.append(dataentry)     }      let linechartdataset = linechartdataset(yvals: dataentries, label: "number of points")     let linechartdata = linechartdata(xvals: xvals, dataset: linechartdataset)     linechart.data = linechartdata } 

finally, supply more information, cause of arrays being reset because implemented viewwillappear function. here is:

override func viewwillappear(animated: bool) {     super.viewwillappear(animated)     self.refreshview() } 

here refreshview function:

 func refreshview() {     self.networking.findemployeeforloggedinuser { (array, error) -> void in         if error != nil {             let alert = uialertcontroller(title: "error", message: "\(error)", preferredstyle: .alert)             let alertaction = uialertaction(title: "ok", style: .cancel, handler: nil)             alert.addaction(alertaction)             self.presentviewcontroller(alert, animated: true, completion: nil)         } else {             dispatch_async(dispatch_get_main_queue(), { () -> void in                 self.namelabel.text = self.employee.name                 self.title = self.employee.name                 self.rolelabel.text = self.employee.jobdesc                 self.educationlabel.text = self.employee.education                 self.birthdaylabel.text = self.employee.birthday                 self.commentarytextview.text = self.employee.commentary                 self.emailtextview.text = self.employee.email             })         }     }      self.networking.fetchimageforemployee(employee, completion: { (error, image) -> void in         self.imageactind.activityindicatorviewstyle = uiactivityindicatorviewstyle.white         self.image.addsubview(self.imageactind)          self.imageactind.settranslatesautoresizingmaskintoconstraints(false)         self.view.addconstraint(nslayoutconstraint(item: self.imageactind, attribute: .centerx, relatedby: .equal, toitem: self.image, attribute: .centerx, multiplier: 1.0, constant: 0.0))         self.view.addconstraint(nslayoutconstraint(item: self.imageactind, attribute: .centery, relatedby: .equal, toitem: self.image, attribute: .centery, multiplier: 1.0, constant: 0.0))          self.imageactind.startanimating()         self.image.alpha = 0.5          if error != nil {             dispatch_async(dispatch_get_main_queue(), { () -> void in                 self.imageactind.stopanimating()                 self.image.alpha = 1.0             })              let alert = uialertcontroller(title: "error", message: "\(error!)", preferredstyle: .alert)             let alertaction = uialertaction(title: "ok", style: .cancel, handler: nil)             alert.addaction(alertaction)             self.presentviewcontroller(alert, animated: true, completion: nil)         } else {             dispatch_async(dispatch_get_main_queue(), { () -> void in                 self.imageactind.stopanimating()                 self.image.alpha = 1.0                 self.image.image = image             })         }     }) } 

i don't know why these arrays being reset being empty. doing wrong?

[this assumes code running inside single uiviewcontroller instance.]

i think misunderstand aspects of uiviewcontroller lifecycle. viewdidload() called once, during app's startup sequence, when none of ui visible, no components have been laid out, , no timers have been given chance start. unless you're loading data in persistent store (disk; database; etc.) @ point, arrays have values set overriding constructor (if have one) or otherwise have values set class-level declaration initializers.

when start nstimer, , when expect go off?

are using println()s or debugging breakpoints teach true sequence of events?

i have add you're doing ui code off main thread, big no-no. presentation of alerts must follow same dispatch pattern non-error ui paths.