ios - Explicitly declare getter '-newRelationship' with '__attribute__((objc_method_family(none)))' to return an 'unowned' object mogenerator -

i'm getting error

explicitly declare getter '-newrelationship' 'attribute((objc_method_family(none)))' return 'unowned' object

when attempting access property

@property (nonatomic, strong) nsstring* newborntyperawvalue; 

in extension on subclass. i'm using coredata , mogenerator. superclass generated mogenerator, in swift extension on subclass have following code

extension subclassname {     var newborntype: differenttype? {          {             willaccessvalue(forkey: "newborntyperawvalue")             let storedstringop = primitivenewborntyperawvalue()             didaccessvalue(forkey: "newborntyperawvalue")              if let storedstring = storedstringop {                 return differenttype(storedstring)             } else {                 return nil             }         }          set {              guard let newvalue = newvalue else {                 willaccessvalue(forkey: "newborntyperawvalue")                 setprimitivenewborntyperawvalue(nil)                  self.didaccessvalue(forkey: "newborntyperawvalue")                 return             }              let rawvalue = newvalue.rawvalue //this returns string              willaccessvalue(forkey: "newborntyperawvalue")             setprimitivenewborntyperawvalue(rawvalue)             didaccessvalue(forkey: "newborntyperawvalue")          }     } }