Instance member cannot be used on type

Question

I have the following class   class ReportView  NSView         var categoriesPerPage     Int         var numPages  Int     return categoriesPerPage count       Compilation fails with the message      Instance member  categoriesPerPage  cannot be used on type    ReportView    What does this mean

User · Answer

It is saying you have an instance variable (the var is only visible/accessible when you have an instance of that class) and you are trying to use it in the context of a static scope (class method).

You can make your instance variable a class variable by adding static/class attribute.

You instantiate an instance of your class and call the instance method on that variable.

User · Answer

I kept getting the same error inspite of making the variable static  Solution  Clean Build  Clean Derived Data  Restart Xcode  Or shortcut  Cmd   Shift Alt K  UserNotificationCenterWrapper delegate   self  public static var delegate  UNUserNotificationCenterDelegate            get               return UNUserNotificationCenter current   delegate                   set               UNUserNotificationCenter current   delegate   newValue

User · Answer

Sometimes Xcode when overrides methods adds class func instead of just func  Then in static method you can t see instance properties  It is very easy to overlook it  That was my case

User · Answer

Just in case someone really needs a closure like that  it can be done in the following way   var categoriesPerPage     Int     var numPagesClosure    - gt Int       return           return self categoriesPerPage count

User · Answer

You just have syntax error when saying    return self someValue   The   isn t needed    Use    var numPages  Int       get          return categoriesPerPage count            if you want get only you can write  var numPages  Int        return categoriesPerPage count     with the first way you can also add observers as set willSet  amp  didSet  var numPages  Int       get          return categoriesPerPage count           set v          self categoriesPerPage   v           allowing to use   operator as a setter  myObject numPages   5

User · Answer

Your initial problem was   class ReportView  NSView     var categoriesPerPage     Int       var numPages  Int     return categoriesPerPage count          Instance member  categoriesPerPage  cannot be used on type  ReportView    previous posts correctly point out  if you want a computed property  the   sign is errant   Additional possibility for error   If your intent was to  Setting a Default Property Value with a Closure or Function   you need only slightly change it as well   Note  this example was obviously not intended to do that   class ReportView  NSView     var categoriesPerPage     Int       var numPages  Int     return categoriesPerPage count         Instead of removing the    we add    to denote a default initialization closure   This can be useful when initializing UI code  to keep it all in one place    However  the exact same error occurs      Instance member  categoriesPerPage  cannot be used on type  ReportView    The problem is trying to initialize one property with the value of another  One solution is to make the initializer lazy  It will not be executed until the value is accessed   class ReportView  NSView     var categoriesPerPage     Int       lazy var numPages  Int     return categoriesPerPage count         now the compiler is happy

User · Answer

For anyone else who stumbles on this make sure you re not attempting to modify the class rather than the instance   unless you ve declared the variable as static   eg    MyClass variable    Foo     WRONG  - Instance member  variable  cannot be used on type  MyClass   instanceOfMyClass variable    Foo     Right

User · Answer

Another example is  you have class like      obc class Album  NSObject       let name String     let singer Singer     let artwork URL     let playingSong Song                   class func getCurrentlyPlayingSongLyric duration  Int   0  - gt  String                         return playingSong lyric           you will also get the same type of error like    instance member x cannot be used on type x     It s because you assign your method with  class  keyword  which makes your method a type method  and using like      Album getCurrentlyPlayingSongLyric duration  5    but who set the playingSong variable before  Ok  You shouldn t use class keyword for that case              func getCurrentlyPlayingSongLyric duration  Int   0  - gt  String                         return playingSong lyric               Now you re free to go

[swift] Instance member cannot be used on type

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