ios - iCloud Sync check for duplicates Swift -

i'm trying set icloud sync existing coredata app. basic syncing working fine. i'm trying check duplicates when updating store.

i've used the official documentation this thread , tried translate code swift. here i've got far:

func checkduplicates() {      let uniquepropertykey = "titel"     let entityname = "entity"      let keypathexpr = nsexpression(forkeypath: uniquepropertykey)      let countexpr: nsexpression = nsexpression(forfunction: "count:", arguments: [keypathexpr])     let countexprdesc = nsexpressiondescription()     countexprdesc.name = "count"     countexprdesc.expression = countexpr     countexprdesc.expressionresulttype = nsattributetype.integer64attributetype      let entity: nsentitydescription = nsentitydescription.entityforname(entityname, inmanagedobjectcontext: moc)!     let uniqueattr: nsattributedescription = (entity.attributesbyname[uniquepropertykey]! as? nsattributedescription)!      let sortdescriptor = nssortdescriptor(key: "timestamp", ascending: true)      let fr = nsfetchrequest(entityname: entityname)     fr.resulttype = nsfetchrequestresulttype.dictionaryresulttype     fr.propertiestofetch = [uniqueattr, countexprdesc]     fr.propertiestogroupby = [uniqueattr]     fr.sortdescriptors = [sortdescriptor]      let fetcheddictionaries: nsarray = self.fetchdictionarieswithrequest(fr)     println(fetcheddictionaries)     var valueswithdupes: nsmutablearray?      dict in fetcheddictionaries {         let count: int = dict["count"] as! int         if count > 1 {             valueswithdupes!.addobject(dict[uniquepropertykey]!!)         }     }      println(valueswithdupes)     let dupefr = nsfetchrequest(entityname: entityname)     dupefr.includespendingchanges = false     dupefr.fetchbatchsize = 20     let predicate = nspredicate(format: "\(uniquepropertykey) in %@", valueswithdupes!)     dupefr.predicate = predicate      let dupes: nsarray = self.fetchdictionarieswithrequest(dupefr)      println(dupes)  }  func fetchdictionarieswithrequest (request: nsfetchrequest) -> nsarray {     var fetchedresultscontroller = nsfetchedresultscontroller(fetchrequest: request, managedobjectcontext: moc, sectionnamekeypath: nil, cachename: nil)     println(fetchedresultscontroller.fetchedobjects)      var error: nserror? = nil      if fetchedresultscontroller.performfetch(&error) {         println("error when fetching records: \(error)")         return nil     }      return fetchedresultscontroller.fetchedobjects!  } 

first , obvious problem error check in fetchdictionarieswithrequest cannot return nil here

second fetchedresultscontroller returns nil. how fetchrequest looks in logs:

    <nsfetchrequest: 0x1744c4280> (entity: entity; predicate: ((null)); sortdescriptors: ((     "(timestamp, ascending, compare:)" )); type: nsdictionaryresulttype; includespendingchanges: no; propertiestofetch: ((     "(<nsattributedescription: 0x17012b040>), name titel, isoptional 1, istransient 0, entity entity, renamingidentifier titel, validation predicates (\n), warnings (\n), versionhashmodifier (null)\n userinfo {\n}, attributetype 700 , attributevalueclassname nsstring, defaultvalue (null)",     "(<nsexpressiondescription: 0x170171f40>), name count, isoptional 1, istransient 0, entity (null), renamingidentifier count, validation predicates (\n), warnings (\n), versionhashmodifier (null)\n userinfo {\n}" )); propertiestogroupby: ((     "(<nsattributedescription: 0x17012b040>), name titel, isoptional 1, istransient 0, entity entity, renamingidentifier titel, validation predicates (\n), warnings (\n), versionhashmodifier (null)\n userinfo {\n}, attributetype 700 , attributevalueclassname nsstring, defaultvalue (null)" )); ) 

however i'm stuck. have typos in code? did translate wrong objective-c? know of working example of in swift somewhere in net?

any appreciated!

thx seb