ios - NSFetchedResultsController -[__NSArrayM insertObject:atIndex:]: object cannot be nil -

i've done quite bit of research on issue, found nothing lead me solution. attempting use nsfetchedresultscontroller, , getting error when run app:

* terminating app due uncaught exception 'nsinvalidargumentexception', reason: '* -[__nsarraym insertobject:atindex:]: object cannot nil' *** first throw call stack:

i have found people encountered problem when using estimatedheightforrowatindexpath method, i'm not using it.

using exception breakpoint revealed it's crashing @ line in below block of code: let frc = nsfetchedresultscontroller(fetchrequest: fetchrequest, managedobjectcontext: self.managedcontext, sectionnamekeypath: "date.thedate", cachename: nil). doesn't make past here.

i have print statement below never executes. managedobjectcontext exist. frc called first time in viewdidload (code below). i'll include appdelegate code.

thanks in advance!

here's relevant code:

import uikit import coredata  class transactionsviewcontroller: uiviewcontroller, uitableviewdatasource, nsfetchedresultscontrollerdelegate {      var containerdelegate: containerdelegate?      var managedcontext: nsmanagedobjectcontext!      lazy var frc: nsfetchedresultscontroller = {         // initialize fetch request         let fetchrequest = nsfetchrequest(entityname: "dailytransactions")          // initialize fetched results controller         let frc = nsfetchedresultscontroller(fetchrequest: fetchrequest, managedobjectcontext: self.managedcontext, sectionnamekeypath: "date.thedate", cachename: nil)          print("assigned frc complete.")          // configure fetched results controller         frc.delegate = self          print("frc finished")          return frc     }() 

frc first used in viewdidload this:

    // exectue fetch request     {         try self.frc.performfetch()     } catch {         let fetcherror = error nserror         print("\(fetcherror), \(fetcherror.userinfo)")     } 

update:

after using sort descriptions on fetch request , changed section key path nil, resolved issue. can change section key path date.thedate , run fine.

your managed context zero. therefore don't anything. why not initialized, there should context , otherwise objects can't propagated...