ios - NSFetchedResultsController notifies its Delegate of delete changes when a managed object is modified, and never notifies for Insert or Update -

i have uitableviewcontroller, delegate nsfetchedresultscontroller. nsfetchedresultscontrollerdelegate functions set per "typical use" in apple's documentation, table view controller fetched result controller's delegate property.

i have view controllers presented on top of table view managed objects can modified. these modifications done on same managed object context. there 1 managed object context constructed in application, , accessed globally. (i have put print statements in object context construction sure not accidentally re-constructing elsewhere.)

when modify 1 of managed objects, delegate function controller:didchangeobject called, nsfetchedresultschangetype always .delete. when create managed object, delegate function not fire @ all.

however, when manually call call performfetch() , tableview.reloaddata(), cells restored correct state: removed row comes back, not-inserted rows created.

the result deleting object works expected (the cell removed), updates object cause cell removed, , object creations not trigger cell inserts.

i tried create simple demo of behaviour, when re-created situation blank application, don't see behaviour. within application causing strange behaviour, can't figure out what. ideas?

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extra info:

the actual construction of predicate , sort descriptors done on several different classes, printing them via print(resultscontroller.fetchrequest.predicate) , print(resultscontroller.fetchrequest.sortdescriptors) gives following:

optional(readstate == "2" or readstate == "1")

optional([(readstate, ascending, compare:), (title, ascending, compare:)])

i have put print statement in controller:didchangeobject: method, , can see gets called type.rawvalue = 2 (i.e. .delete), , when modify objects, not when create them.

it's inconsistency how nsfetchedresultscontroller handles nspredicate.

if nsfetchedresultscontroller constructed fetch request has predicate comparison between integer , string follows:

let predicate = nspredicate(format: "integerattribute == %@", string(1)) 

this lead predicate string being:

integerattribute == "1"

when case, initial fetches work fine: calling function performfetch() on fetched results controller returns objects integerattribute equal 1 (where integerattribute of type int32).

however, notifications nsfetchedresultscontrollerdelegate not work fine. modifications of managed objects result in delegate being notified of nsfetchedresultschangetype.delete change. creations of managed objects not invoke delegate @ all.

to make weirdness go away, fix predicate format string follows:

let predicate = nspredicate(format: "integerattribute == %d", 1)