ios - NSFetchedResultsController sorts in wrong order -

i working on project based on coredata example xcode. have entity-class named entity updated key stores timestamp entity updated, , nsfetchresultscontroller set sort in descending order:

nsfetchrequest *fetchrequest = [[nsfetchrequest alloc] init]; [fetchrequest setentity:[nsentitydescription entityforname:@"entity" inmanagedobjectcontext:_managedobjectcontext]]; [fetchrequest setfetchbatchsize:20]; [fetchrequest setsortdescriptors:@[[[nssortdescriptor alloc] initwithkey:@"updated" ascending:no]]];  nsfetchedresultscontroller *frc = [[nsfetchedresultscontroller alloc] initwithfetchrequest:fetchrequest managedobjectcontext:_managedobjectcontext sectionnamekeypath:nil cachename:nil]; 

this works fine on initial load, when insert nsmanagedobject should inserted in between other objects, gets inserted @ top. when relaunch app, gets inserted @ right position.

e.g: table like:

updated: 300 updated: 200 updated: 100 

and when insert managedobject: updated: 250, expect table like:

updated: 300 updated: 250 <-- inserted here updated: 200 updated: 100 

but get:

updated: 250 <-- inserted @ top updated: 300 updated: 200 updated: 100 

is how nsfetchresultscontroller works, or there way re-sort nsmanagedobjects on every insert? :)

in default, new object inserted top. should keep index of every objects if customize sort. can sort objects in way.