Xcode - How to fix NSUnknownKeyException reason this class is not key value coding-compliant for the key X error

Question

I m trying to link a UILabel with an IBOutlet created in my class   My application is crashing with the following error    What does this mean    How can I fix it          Terminating app due to uncaught exception  NSUnknownKeyException   reason     lt UIViewController 0x6e36ae0  setValue forUndefinedKey    this class is not key value coding-compliant for the key XXX

User · Answer

I resolved this problem by doing 2 things    Fixed Class reference of the view       Reimported all Outlets

User · Answer

Sometimes swift file are not added or removed from target  go to target-- Build setting --  compile Sources --  see if any required swift class file is missing or not    In my case Application was crashing due to swift source file not present in compile

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Sometimes this has to do with your  Inherit From Target  That value has to be set  With single target apps you can just select Inherit From Target  If you have more then one target select the desired target

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Another tricky case   In IB added ViewController to storyboard  deleted its view and set Custom Class to  MyViewController  so view is instantiated from MyViewController xib  Specifying Storyboard ID the same  MyViewController  causes exception   Changing Storyboard ID to some different name resolves the issue

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Your view controller may have the wrong class in your xib   I downloaded your project    The error you are getting is       NSUnknownKeyException   reason     lt UIViewController 0x3927310  setValue forUndefinedKey    this class is not key value coding-compliant for the key string     It is caused by the Second view controller in MainWindow xib having a class of UIViewController instead of SecondView  Changing to the correct class resolves the problem    By the way  it is bad practice to have names like  string  in Objective-C  It invites a runtime naming collision  Avoid them even in once off practice apps  Naming collisions can be very hard to track down and you don t want to waste the time    Another possible reason for this error  when copying  amp  pasting elements from one controller into another  Xcode somehow keeps that link to the original controller  even after editing  amp  relinking this element into the new controller   Another possible reason for this error   Bad Outlet   You have either removed or renamed an outlet name in your  h file   Remove it in  xib or  storyboard file s Connection Inspector   One more possible reason     In my case  Extension of UIView with bindable properties and setting values for those bindable properties  i e  shadow  corner radius etc   then remove those properties from UIView extension  for some reason  but the following  lt userDefinedRuntimeAttributes gt  remained in xml  of foo storyboard     lt userDefinedRuntimeAttributes gt     lt userDefinedRuntimeAttribute type  color  keyPath  shadowColor  gt         lt color key  value  white  0 0  alpha  1  colorSpace  custom  customColorSpace  genericGamma22GrayColorSpace   gt     lt  userDefinedRuntimeAttribute gt     lt userDefinedRuntimeAttribute type  number  keyPath  shadowOpacity  gt         lt real key  value  value  50   gt     lt  userDefinedRuntimeAttribute gt     lt userDefinedRuntimeAttribute type  point  keyPath  shadowOffset  gt         lt point key  value  x  5  y  5   gt     lt  userDefinedRuntimeAttribute gt     lt userDefinedRuntimeAttribute type  number  keyPath  shadowRadius  gt         lt real key  value  value  16   gt     lt  userDefinedRuntimeAttribute gt     lt userDefinedRuntimeAttribute type  number  keyPath  borderWidthValue  gt         lt real key  value  value  0 0   gt     lt  userDefinedRuntimeAttribute gt   lt  userDefinedRuntimeAttributes gt    Solution  Right click on foo storyboard   Open as Source Code   search by keyPath  i e  shadowRadius    Delete the  lt  userDefinedRuntimeAttributes gt  that causing the problem

User · Answer

I had the same error in yet another slightly different form   In interface builder  I have a navigation controller with a custom subcontroller  The class name of this was set correctly  however the NIB name  select subcontroller  go to Attributes Inspector  was set to the wrong file  basically to one of a different target   Resetting this to the correct filename solved the issue

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I deleted the property from the header file  I couldn t find any reference to it but the debug error was still referencing it  I found that the nib file still had a reference to it  I deleted the block that referenced it and everything was fixed   In Project Navigator   Find the Nib  xib  file  Right click and View Source  I deleted the the following full section   lt object class  IBConnectionRecord  gt       lt object class  IBCocoaTouchOutletConnection  key  connection  gt           lt string key  label  gt DeleteLabel lt  string gt           lt reference key  source  ref  372490531   gt           lt reference key  destination  ref  774585933   gt       lt  object gt       lt int key  connectionID  gt 20 lt  int gt   lt  object gt

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I had the same issue  and the cause was due to specifying a Module in Interface Builder  as opposed to leaving it blank   So  when I was using either a different module than the one I set  the app would crash  S     hope this helps someone else  as my issue was not due to a broken or out-of-date outlet

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In my case  this was caused by referencing the wrong Nib   BMTester  viewController     BMTester alloc  initWithNibName   WrongNibName  bundle nil

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Another one cause of this situation is that you declare this property implemented as  dynamic  but class can not find it in parent class

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In my case  I had added a ViewController to the storyboard  but I didn t assign it a Storyboard ID in the designer    Once I gave it an ID  it worked   using Xamarin Visual Studio 2015

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Did you leave your picker object unconnected   lol 54 answers and not one of them is my solution  Talk about a common error    In my case it was because I had a picker object on my VC and had not set an outlet and action for it   I often leave buttons etc unconnected when I am just looking to see how the layout looks  But it seems you cannot do this for a picker

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I had the same symptom  The root cause was that the  Target Membership  for my source file was not set to the correct target  I assume that means my class wouldn t get built and included in my app   To correct it    Highlight your  m file  In the right pane  select the File Inspector  Under the  Target Membership  section  make sure the appropriate build target is checked    Hope this helps somebody out there

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I encounter the same error log when dealing with my tableview cell  I found that my UILabels have duplicated referencing outlets you could check it out in the reference inspector  to both the file s owner and my cell s class  Things get well when I delete the reference to the file s owner

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Looking over the other answers it seems like there are a lot of things that can cause this error  Here is one more    If you   have a custom view added an  IBInspectable property and then later deleted it    Then you may also get an error similar to      Failed to set  xxx  user defined inspected property on  Your Custom   View       this class is not key value coding-compliant for the key    xxx     The solution is to delete the the old property     Open the Identity inspector for your class  select the property name under User Defined Runtime Attributes  and press the minus button  -

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It can come from the fact that you have control dragged and created an outlet or action  and forgot to delete it  Even if you deleted the code  or even if you have made enough cmd Z  you ll need to go in the connection inspector of your storyboard and see if the action or outlet you created is still here or not

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If it is an iPhone only app  not a universal one  make sure the following field is empty   Targets   Summary   iPhone iPod Deployment Info   Main Interface  If you specify an xib there it crashes

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Same issue presented   My solution was to put the correct storyboard value in the Main Storyboard drop down    I had renamed mainstoryboard storyboard  but not reset the deployment info

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This also happens to me when an UI label or other UI element is referenced by two variables in the view controller class and I delete one of the variable

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I had the same problem and while TechZen s answer may indeed be amazing I found it hard to apply to my situation    Eventually I resolved the issue by linking the label via the Controller listed under Objects  highlighted in the image below  rather then via the File Owner    Hope this helps

User · Answer

I had this error when I was trying to implement a custom ViewCell for a table   When I highlighted View controller for the XIB and connected to the elements in the CellView caused the error   this class is not key value coding-compliant for the key  once I deleted these it got rid of the error   Delete the connections in the below image    Just make sure that you only have the connections with the Table View Cell   To check click on table view cell and in INSPECTOR look for your connections

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My problem started after i changed the Target name   My own custom UI classes had the Module name set to the old target name   I changed the target name to the new one and  it works fine now

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This error indicates that an already connected Interface Builder object is removed renamed in its owner s source  File s Owner     Control-click on the Files s Owner in the Interface Builder if you see a exclamation mark you need to fix that    In the picture below you can see that  aRemovedView  has an exclamation mark on its right  that s because I removed the IBOutlet view object while it was already connected in the IB     This gives the following error  Terminating app due to uncaught exception  NSUnknownKeyException   reason     setValue forUndefinedKey    this class is not key value coding-compliant for the key aRemovedView

User · Answer

Check if you have stray Referencing Outlets by selecting the offending object in the Storyboard xib interface and opening the Connections Inspector  View- Utilities- Show Connections Inspector   If you do remove the unwanted connections and you should be good to go

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this class is not key value coding-compliant for the key  I know its a bit late but my answer is different so I thinks it needs to be posted  I was pushing the second controller in wrong way  Here is sample  Wrong Way to Push Controller  UIViewController  controller     UIViewController  alloc initWithNibName   TempViewController  bundle nil             self navigationController pushViewController controller animated true     Correct way  TempViewController  controller     TempViewController  alloc initWithNibName   TempViewController  bundle nil             self navigationController pushViewController controller animated true     I did not found any answer like above so may be it can help some one having same issue

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I had exact same error message and thanks      to Kira from http   www idev101 com I was able to solve the challenge  I only found her site after googling and stacking over all these threads  I m now posting here for the next one that comes to StackOverFlow and has the same challenge I had since that person will most likely come to this thread over Google   I realized  that I wrongly made this   UIViewController  deviceViewController     UIViewController alloc  initWithNibName   DeviceViewController  bundle nil     Instead of THIS   DeviceViewController  deviceViewController     DeviceViewController alloc  initWithNibName   DeviceViewController  bundle nil     Where  DeviceViewController   Was the name of my Class also known as   DeviceViewController h  DeviceViewController m   You ll have to    import DeviceViewController h    in your implementation   m File  where you want to call e g  another UIViewController   I am absolutely not sorry if I am only stating the obvious for beginners like me and may get down votes as this is not exactly related to the question but I was searching 4       hours straight now for the answer to these error message  If I can spare this to 1 or 2 people that d be great     PS  For those interested in how the code continues for loading the other UIViewController        self presentViewController deviceViewController animated YES completion nil

User · Answer

I was getting this error with storyboards   The above solution didn t seem to be the problem so I ended up deleting the view controller and adding it back in again  and of course reconnecting the segue and reassigning the class  which fixed it   I don t know what it really was  but I had renamed the associated view controller class shortly before this started  so maybe that had hosed something

User · Answer

You may have outlets to UI Element but not IBOutlet property in  h FileFor all UI element in Connection Attribute check outlets and it corresponding property in  h header file   May be missing one or more property entry in  h file

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I just had this issue in my duplicated project and solved by checking 2 places     1- Make sure you have the  m file in the list -  Project - Build Phases - Compile Sources 2- After that  go to interface builder  probably this is an error occures with only IB  and unlink all properties  labels  images  etc    Then re-link all  I have realized that I ve removed an attribute but it was still linked in IB     Hope it works for some

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I had this problem too   I had copied a view with an IBOutlet from one xib file to another xib file   And even though I had removed the old reference and create a new reference  this error was still occurring   I ended up restarting xcode to fix this problem

User · Answer

To add to this epic saga of a thread       My view controller had an attribution above it   objc TheNameOfMyViewController    This made all the Outlets crash with  not key value compliant  error for each Outlet   This was only an issue on IOS12 and below   It worked fine on iOS 13    Removing that modifier fixed this problem   All the outlets are working fine now

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Another  not compliant  issue I found was when I managed to have two copies of a class for some reason     I was adding keys to the wrong copy   Interface Builder still saw the keys and let me hook up to them  but at runtime it was using the other copy of the class that didn t have the new keys     To find which was the  right  copy I used XCode s cmd-click on the class name elsewhere to jump to the correct copy  then I killed off the bad unused copies  after bringing over my edits from the un-used copy first    Moral of the story  duplicate class files are bad

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I got the same error when I manually loaded a view from a nib  It turns out that  I had forgotten to set the view s owner    For e g  If you load a view in the following way     let view   Bundle main loadNibNamed  MyNibFileName                                    owner  nil                                   options  nil   first as  UIView   and then add an IBOutlet  the IBOutlet can t be referenced and the application will crash with the above error   Fix  Assign an owner for the view     let view   Bundle main loadNibNamed  MyNibFileName                                    owner  self                                   options  nil   first as  UIView

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I had this happen when i had a UIView linked into a storyboard and connected IBOutlet like    property  strong  nonatomic  IBOutlet UIView  someView   but later on  i made the UIView into a custom class but forgot to change the class name of this IBOutlet defined above  its a strange error because if the custom view has no subviews it doesnt complain  but as soon as there are subviews it shows the error stated in the question but on one of the subviews and not the outer UIView where the problem actually exists  had me deleting and readding all the subviews trying to find the problem  when in fact had nothing to do with the subviews

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This has already happened to me twice   The solution was remaking the whole storyboard since I copied it from another one  because it was almost the same

User · Answer

This error is something else   Here is how i Fixed it  I m using xcode Version 6 1 1 and using swift  I got this error every time my app tried to perform a segue to jump to the next screen  Here what I did    Checked that the button was connected to the right action  This wasn t the problem  but still good to check  Check that the button does not have any additional actions or outlets that you may have created by mistake   This wasn t the problem  but still good to check  Check the logs and make sure that all the buttons in the NEXT SCREEN have the correct actions  and if there are any segues  make sure that they have a unique identifier   This was the problem   One of the segues did not have a unique identifier One of the buttons had an action and two outlets that I created by mistake  Delete any additional outlets and make sure that you the segues to the next screen have unique identifiers     Cheers

User · Answer

I found another possibility that may cause the issue   When using  initWithNibName  method with the wrong xib name  it will lead to this kind of crash too   Such as you choose to change a xib file s name  and then foget to change the name used in  initWithNibName  method to the same name

User · Answer

You may need to delete the outlet   recreate it by drawing form IB to  H file

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I had this problem with swift classes after upgrading to xcode7  Solved it by using the  objc directive    objc XXXViewController  class XXXViewController

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Just pay attention if you re trying to observe a value that doesn t exist   This happened to me simply as I was observing the  Text  property of a text field when I was supposed to be observing the  text  property instead

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Make sure you add the custom class   even empty  implementation in the  m file like    implementation MySubclass  end

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The cause of my trouble  was that I duplicated a storyboard file  outside of Xcode if I recall correctly   then all view controllers in the duplicated file had same object-ID as in the original file  The remedy is to copy-pasted the view controllers  and they will then get a new object-ID  You can see the object-ID in the Identity Inspector

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I had the same kind of problem  I created a tableviewCell in a XIB file and was getting that kind of error  My problem was that I defined the  File s Owner  class to be my cell view controller  I just took it out and set the cell s class  on the xib file click the  border of the cell  go to the third tab on the right panel and where it says class chose your view controller    Also try cleaning your code

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If you have a custom UIViewController subclass with IBOutlets that are causing problems the only set of steps I found to actually get rid of the error were   1 Change the class to UIViewController   2 Disconnect all the outlets  they will all have the yellow warning triangle now  - it may be enough just to disconnect the problematic outlet s     3 Do all the standard steps -   K  delete Derived Data    prayer mats  worry beads    4 Launch the app - go to the problematic scene    5 Kill the app  go back to Interface Builder change the class back to your custom class name    6 Reconnect your outlets   Launch the app  amp  this will normally have cleared up the key-value compliance issues

User · Answer

In my case it was the module that was specified to the wrong target  Simply deleting the module name and checking Inherit Module from target did the trick

User · Answer

Module  property of View Controller in the Identity Inspector might be different than what you expected  Also make sure that new classes are added to your target list

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Along with other issues that you can see in other answers  The way I created this error for myself was that I started a project from scratch and begin by deleting the initial scene of my storyboard and then pasted a scene from another project into my storyboard   There is no problem in doing that  You only need to add an entry point of your storyboard i e  check the is initial View Controller on which ever view controller you like  Otherwise it will be a gray scene and throw you an error

User · Answer

I had this problem with storyboard and swift class for ui view controller  Solved it by using the  objc directive    objc MyViewController  class MyViewController

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I remember having a similar problem in the past  I solved it by changing the line    vicMain     UIViewController alloc  initWithNibName   vicMainScreen  bundle nil     into    include  vicLogin iPad h           This is the H file of the class holding the code for                                     processing all the IBOUtlets for the Login screen         vicMain     vicLogin iPad alloc  initWithNibName   vicMainScreen  bundle nil     Notice that I was initially declaring UIViewController to init my  vicMain  after using a pop-up window on top  I realised that both are using the same UIViewController   By   1  INCLUDing your class  of the sub-view   along with the same module that is doing the above  vicMain  which is a view controller object variable  i e  it s  vicLogin iPad h  in my case   and   2  Use the your custom constructor to declare the object  i e  instead of  xxx    UIViewController alloc         you use  xxx    vicLogin iPad alloc        instead    the problem is resolved   I hope this helps as it was a pain to pinpoint with the lack of details from the error message     Regards Heider Sati

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That might be the case of referencing a component from Xib Interface that you have renamed or delete  Re-referencing works for me

User · Answer

This was happening to me only when debugging on a device  iPhone   The iOS Simulator was working OK  Doing a  Product- Clean  from Xcode seemed to solve the problem  but I have no idea why

User · Answer

I also had this problem  it was due to renaming a view by creating a new outlet to it  Your might have the old connection outlet in the storyboard    What you need to do is to remove the old outlet from the storyboard    Goto the storyboard  Click  Show Code Review  button  the one the  lt - -  sign on it  just left of the show hide navigator   Search for the  connections  tag  Look for the  outlet  tag within the  connections  tag with the  property  attribute set to the name you are getting in the Exception  Remove that outlet tag  Hit  Command   B   Enjoy

User · Answer

My fix was similar to Gerard Grundy s  In creating a custom UITableViewCell using an XIB  I had mistakenly applied the Custom Class name to the File s Owner instead of to the UITableViewCell  Applying the class to the UITableViewCell on the canvas and connecting my IBOutlet properties to it solved the issue

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Really stupid mistake with me  So I decided to share here  hope this will help another people like me    I have another submodule in my project  and I name a new class with same name with another class in main module  my new class NOT have xib file 100  by code   but another class in main module have xib file  I think Xcode linked wrong the new class with the xib file in main module    That the reason for crash with message   this class is not key value coding-compliant for the key tableView

User · Answer

In my case  I didn t have missing outlets in xib-files after merging      Shift   Command   K   solved my problem  I cleaned my project and rebuilt

User · Answer

I had the same issue when I was using the main storyboard as the launch screen file  I guess if you are using a storyboard as the launch screen file  it shouldn t be connected to the view controller as it won t have been loaded yet

User · Answer

I had the same issue This happened with my project because I changed my product name but in interface builder I had the old name as Module  this leads to crash so be sure to check all the xib module name also has been changed or not

User · Answer

I had to delete the app from the simulator iPhone to get rid of this error

User · Answer

in my case it was an error in the storyboard source code  follow these steps    first open your story board as source code   search for  lt connections gt  remove unwanted connections   For example    lt connections gt       lt outlet property  mapPostsView  destination  4EV-NK-Bhn  id  ubM-Z6-mwl   gt       lt outlet property  mapView  destination  kx6-TV-oQg  id  4wY-jv-Ih6   gt       lt outlet property  sidebarButton  destination  6UH-BZ-60q  id  8Yz-5G-HpY   gt   lt  connections gt    As you see  these are connections between your code variables  names and the storyboard layout xml tags

User · Answer

I ran into the same problem for a different reason  I was using the main storyboard as the launch screen file  I guess if you are using a storyboard as the launch screen file  it shouldn t be connected to the view controller as it won t have been loaded yet

User · Answer

I had a similar problem for a project that has two targets  with their own MainWindow XIB   The fundamental issue that caused this error for me was that the UIViewController class wasn t included in the second project s resource list  I e  interface builder allowed me to specify it in MainWindow xib  but at runtime the system couldn t locate the class   I e  cmd-click on the UIViewController class in question and double-check that it s included in the  Targets  tab

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It could mean you re trying to use a sort descriptor without an atsign at the beginning  As in     array valueForKeyPath   distinctUnionOfObjects self    Which must actually be    array valueForKeyPath    distinctUnionOfObjects self

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In my case     NSBundle mainBundle  loadNibNamed   NameOfTheSubviewNibFile  owner self options nil    was the reason   replacing this with initWithNibName  resolved

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Just to add to this  because I was getting this error as well  Going through all these answers most seem to apply to working with the UI and storyboard stuff  I know the original poster did seem to be working with the UI but when searching for possible reasons for this error mostly all questions lead back to this question with those others being closed as duplicates or simply having issues with connecting things in a storyboard so I will add my solution   I was working on coding a web service in Swift 2  I had built all the needed proxy objects and stubs  As I looped through the returned XML I was dynamically instantiating my objects  which all came from NSObject and using setValue forKey on them  Every time setValue forKey tried to set a property it blew up with this error   I had a switch statement for each type I was dealing with  e g  Bool   CShort   String   and for each XML node I went through and checked what the type was on the object and then converted the value to that type and attempted to set it with setValue forKey   Eventually I started commenting out all these setValue forKey lines and found that my default switch statement case did work for String    I finally figured out that you can t use optional swift types with setValue forKey unless they have a direct mapping to an Objective-C type like String  or NSNumber   I ended up changing all CShort  types to NSNumber  since that has a direct mapping  For Bool  in my case it was fine for me to just use Bool and initialize it to false  Others may not have that luxury   Anyway what a headache that was so hopefully this helps someone else who has a similar problem and keeps getting redirected to this question and saying to themselves   I am not doing anything in UI      So lastly to reiterate one more time Key-Value Coding does not work with optionals  Below I ended up finding somewhere but I forget where so to whoever posted this I apologize and would give credit if I remembered where I found this but it saved my life      You cannot use KVC on an Optional Int property  because KVC is Cocoa     Objective-C  and Objective-C cannot see an Optional Int - it is not   bridged to Objective-C  Objective-C can only see types that are   bridged to Objective-C       class types that are derived from NSObject      class types that are exposed with  objc      Swift structs that are bridged

User · Answer

I got the same problem  I did resetting the simulator  Removing and adding button control  and finally made a clean     Thanks to stack overflow  Some how my code became ok and starting working

User · Answer

This happens to me when my view controller originally had an  xib file  but now is created programmatically   Even though I have deleted the  xib file from this project  The users iPhone iPad may contain an  xib files for this viewcontroller   Attempting to load an  xib file usually causes this crash   Terminating app due to uncaught exception  NSUnknownKeyException   reason     lt UIViewController 0x18afe0 gt  setValue forUndefinedKey    this class is not key value coding-compliant for the key welcomeLabel     Solution when creating it programmatically may be this   - void loadView          Ensure that we don t load an  xib file for this viewcontroller     self view    UIView new

User · Answer

You only need to specify IBOutlet once  the IBOutlet label your ivar is unnecessary  Are you instantiating your NIB using your UIViewController  At some point you should be calling  SecondView initWithNibName   yourNibName  bundle nil

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I encountered this error that occurred on all outlets in a custom class I had created for a table view prototype cell   The outlets were all correctly connected to the storyboard  and the Class field was correctly named in the identity inspector for the prototype cell     Deleting and recreating the outlets did not work   Cleaning the build did not work  What finally worked was to change the Class in the storyboard identity inspector to the default UITableViewCell  hit Enter  then change it back to the name of my custom class afterwards   For some reason  this worked

User · Answer

Usually when this happens to me   TechZen s answer does the trick  Yesterday  however  I spent an embarrassingly long time mucking with storyboard connections only to discover that the problem was in my code   I have a custom view controller that handles various layouts in my storyboard  but one of the layouts needed a special label not used by the others  So I created a subclass like so    interface MyViewControllerSubclass   MyViewController   Then I added a private property in MyViewControllerSubclass m    interface MyViewController     property  weak  nonatomic  IBOutlet UILabel  crashesApp   end   Xcode happily allowed me to connect this IBOutlet  yet every time the view would load  the app would crash with the old  not key-value compliant for the key  chrashesApp     The solution  which is semi-obvious in retrospect  was to change the private category to use the correct name  i e   that of the subclass    interface MyViewControllerSubclass     property  weak  nonatomic  IBOutlet UILabel  noMoreCrashing   end

User · Answer

You may have a bad connection in your xib   I ve had this error many times  While TechZen s answer is absolutely right in this case  another common cause is when you change the name of a IBOutlet property in your  h  m which you ve already connected up to File s Owner in the nib   From your nib    Select the object in IB and go to the  Connections Inspector   Under  Referencing Outlets  make sure that your object isn t still connected to the old property name    if it is  click the small  x  to delete the reference and build again       Another common cause if you are using Storyboard  your UIButton might have more then one assignings  Solution is almost the same as for nib     Open your storyboard and right click the UIButton You will see that there is more than one assign ref to this button  Remove one of the  Main     greyed windows with the small  x

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In my case it was that an IBOutlet s property name in a ViewController m was changed  but the one in Storyboard was not  Reintroducing the IBOutlet into the ViewController m per ctrl-drag solved the problem  I have also noticed a way to find such  orphane  IBOutlets in XCode   look at the image  the ones that are not  orphaned  have concentric circles instead of line numbers

User · Answer

This problem also happens if you want to design a small subview in a separate XIB file in Interface Builder  and in IB you set it to the same class as the parent view    If you then show it like this    UIViewController  vc     UIViewController alloc  initWithNibName   NameOfTheSubviewNibFile  bundle nil    self view addSubview vc view     The view will appear  but if it s got IBOutlets connected to its File Owner  you ll get the error message  So  this should work instead    In your the parent view s code  declare an IBOutlet UIView  mySubview to reference the view in the subview s nib file In the subview s nib file  connect the File Owner to the view  and set it to mySubview show it by doing       NSBundle mainBundle  loadNibNamed   NameOfTheSubviewNibFile  owner self options nil   self view addSubview mySubview     and you will be fine

[ios] Xcode - How to fix 'NSUnknownKeyException', reason: … this class is not key value coding-compliant for the key X" error?

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