ios - NSFetchedResultsController: no object at index 2147483647 -

need hint, give after spending several hours struggling nsfetchedresultscontroller.

the error message is:

coredata: error: nsfetchedresultscontroller: no object @ index 2147483647 in section @ index 0

...but don't know firing error. last piece of code savecontext(), next breakpoint inside didchange.

class viewcontroller : uitableviewcontroller, nsfetchedresultscontrollerdelegate private lazy var channelcontroller: nsfetchedresultscontroller<zchannel> = {      let appdelegate: appdelegate = uiapplication.shared.delegate as! appdelegate      let request: nsfetchrequest<zchannel> = zchannel.fetchrequest()     request.sortdescriptors = [nssortdescriptor(key: "kit", ascending: true), nssortdescriptor(key: "name", ascending: true)]      let retval: nsfetchedresultscontroller<zchannel> = nsfetchedresultscontroller(fetchrequest: request,                                                                                  managedobjectcontext: appdelegate.persistentcontainer.viewcontext,                                                                                  sectionnamekeypath: "kit",                                                                                  cachename: nil)     retval.delegate = self      return retval }()  public init() {     super.init(style: .grouped)      self.tableview.register(channeltablecell.self, forcellreuseidentifier: "channeltablecell")      let appdelegate: appdelegate = uiapplication.shared.delegate as! appdelegate     appdelegate.persistentcontainer.viewcontext.perform {         {             try self.channelcontroller.performfetch()         } catch {             let e = error nserror             fatalerror("[coredata] unresolved fetch error \(e), \(e.userinfo)")         }     } }      public func controller(_ controller: nsfetchedresultscontroller<nsfetchrequestresult>, didchange anobject: any, @ indexpath: indexpath?, type: nsfetchedresultschangetype, newindexpath: indexpath?) {     switch(type) {     case .insert:         self.tableview?.insertrows(at: [newindexpath!], with: .bottom)         break;     case .update:         self.tableview?.reloadrows(at: [indexpath!], with: .bottom)         break     default:         break     } }  public func controller(_ controller: nsfetchedresultscontroller<nsfetchrequestresult>, didchange sectioninfo: nsfetchedresultssectioninfo, atsectionindex sectionindex: int, type: nsfetchedresultschangetype) {     switch (type) {     case .insert:         self.tableview?.insertsections(indexset(integer: sectionindex), with: uitableviewrowanimation.bottom)         break     case .delete:         self.tableview?.deletesections(indexset(integer: sectionindex), with: uitableviewrowanimation.bottom)         break     default:         break     } } 

from other thread insert new object:

self.persistentcontainer.viewcontext.performandwait {     // ...     let channel: zchannel = nsentitydescription.insertnewobject(forentityname: "zchannel", into: self.persistentcontainer.viewcontext) as! zchannel     // ...     self.savecontext() } 

some issues:

• 2147483647 nsnotfound. if using indexofobject , assuming in array , using index cause of crash.
• you using indexpath row update when should use newindexpath. reason indexpath index before inserts or delete , newindexpath index after inserts , deletes.
• there no reason call self.channelcontroller.performfetch() inside persistentcontainer.viewcontext.perform on main thread