ios - UIDatePicker crashing application -

in app have textfield form want populated date picker, have assigned date picker input view textfield , datepickervaluechanged func change text of textfield when picker changed. issue when clicking off data picker in app, whole app crashes

'terminating uncaught exception of type nsexception'

any ideas? here code:

@iboutlet var startdatepickerfield: uitextfield!  override func viewdidload() {      let startdatepicker:uidatepicker = uidatepicker()     startdatepicker.datepickermode = uidatepickermode.dateandtime     startdatepickerfield.inputview = startdatepicker     startdatepicker.addtarget(self, action:  #selector(popovertableviewcontroller.datepickervaluechanged(_:)), for: uicontrolevents.valuechanged)  }  func datepickervaluechanged(_ sender: uidatepicker) {      let dateformatter = dateformatter()     dateformatter.datestyle = dateformatter.style.long     dateformatter.timestyle = dateformatter.style.short     startdatepickerfield.text = dateformatter.string(from: sender.date)  } 

this contained in class view controller "popovertableviewcontroller". thanks!

here crash report log:

2016-07-28 12:50:00.956 clockin_v2[5935:2049267] -[clockin_v2.popovertableviewcontroller startdatedidbegin:]: unrecognized selector sent instance 0x7ff571c10720 2016-07-28 12:50:00.961 clockin_v2[5935:2049267] * terminating app due uncaught exception 'nsinvalidargumentexception', reason: '-[clockin_v2.popovertableviewcontroller startdatedidbegin:]: unrecognized selector sent instance 0x7ff571c10720' * first throw call stack: ( 0 corefoundation 0x000000010fe5986b exceptionpreprocess + 171 1 libobjc.a.dylib
0x000000010f4b124e objc_exception_throw + 48 2 corefoundation
0x000000010fec7904 -[nsobject(nsobject) doesnotrecognizeselector:] + 132 3 corefoundation 0x000000010fddfed5 ___forwarding_ + 1013 4 corefoundation 0x000000010fddfa58 _cf_forwarding_prep_0 + 120 5 uikit
0x000000011027aaf0 -[uiapplication sendaction:to:from:forevent:] + 83 6 uikit 0x00000001103fda69 -[uicontrol sendaction:to:forevent:] + 67 7 uikit 0x00000001103fdd82 -[uicontrol _sendactionsforevents:withevent:] + 444 8 uikit 0x0000000110d5b196 -[uitextfield _resignfirstresponder] + 297 9 uikit 0x000000011048d780 -[uiresponder _finishresignfirstresponder] + 286 10 uikit 0x0000000110d5af94 -[uitextfield _finishresignfirstresponder] + 49 11 uikit 0x000000011048d82f -[uiresponder resignfirstresponder] + 140 12 uikit 0x0000000110d5ae63 -[uitextfield resignfirstresponder] + 136 13 uikit
0x000000011048d4bf -[uiresponder becomefirstresponder] + 358 14 uikit 0x0000000110328dae -[uiview(hierarchy) becomefirstresponder] + 138 15 uikit 0x0000000110d59d2e -[uitextfield becomefirstresponder] + 51 16 uikit 0x00000001107af37b -[uitextinteractionassistant(uitextinteractionassistant_internal) setfirstresponderifnecessary] + 206 17 uikit
0x00000001107b2b46 -[uitextinteractionassistant(uitextinteractionassistant_internal) onefingertap:] + 3823 18 uikit
0x00000001107a081d -[uigesturerecognizertarget _sendactionwithgesturerecognizer:] + 57 19 uikit 0x00000001107a85b4 _uigesturerecognizersendtargetactions + 109 20 uikit 0x00000001107a613b _uigesturerecognizersendactions + 540 21 uikit 0x00000001107a539d -[uigesturerecognizer _updategesturewithevent:buttonevent:] + 1177 22 uikit 0x00000001107911f2 _uigestureenvironmentupdate + 1013 23 uikit
0x0000000110790db5 -[uigestureenvironment _deliverevent:togesturerecognizers:usingblock:] + 521 24 uikit 0x000000011078ff2c -[uigestureenvironment _updategesturesforevent:window:] + 286 25 uikit 0x00000001102e945c -[uiwindow sendevent:] + 3989 26 uikit
0x00000001102967a5 -[uiapplication sendevent:] + 281 27 uikit
0x0000000110a632c3 dispatchpreprocessedeventfromeventqueue + 3303 28 uikit 0x0000000110a5be75 __handleeventqueue + 4879 29 corefoundation 0x000000010fdff5d1 __cfrunloop_is_calling_out_to_a_source0_perform_function + 17 30 corefoundation 0x000000010fde485c __cfrunloopdosources0 + 556 31 corefoundation 0x000000010fde3d46 __cfrunlooprun + 918 32 corefoundation
0x000000010fde3754 cfrunlooprunspecific + 420 33 graphicsservices
0x0000000114629a71 gseventrunmodal + 161 34 uikit
0x0000000110278e9c uiapplicationmain + 159 35 clockin_v2
0x000000010eec96df main + 111 36 libdyld.dylib
0x00000001136a968d start + 1 ) libc++abi.dylib: terminating uncaught exception of type nsexception (lldb)

instead of adding action using

startdatepicker.addtarget(self, action:  #selector(popovertableviewcontroller.datepickervaluechanged(_:)), for: uicontrolevents.valuechanged)   

open in assistant editor, open storyboard in 1 part, right click on date picker, in list of events, click on "value changed" (it show little '+' sign when hover upon empty hole in front of it) , extend "popovertableviewcontroller.swift" file.