objective c - Undoing Core Data insertions that are performed off the main thread -

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i'm working on code uses nsoperation import data. i'd user able undo nsmanagedobject instances created during import operation.

from can tell, it's impossible use nsmanagedobjectcontext -undomanager operations performed off of main thread. core data programming guide section on use thread confinement support concurrency, have these 2 conditions:

  1. only objectid should passed between managed object contexts (on separate threads)
  2. managed objects must saved in context before objectid can used.

this makes sense since managed objects need moved private storage (nsmanagedobjectcontext) public storage (nspersistentstore) before can shared.

unfortunately, -save: message causes managed objects in undo stack removed. memory management using core data section of same guide:

managed objects have pending changes (insertions, deletions, or updates) retained context until context sent save:, reset , rollback, or dealloc message, or appropriate number of undos undo change.

i've tried several things work around limitation, , leads bulk of work happening on main thread (and spinning beach balls.) clues getting undo working objects created off main thread appreciated.

--

an enhancement radar has been submitted: rdar://problem/8977725

this answer bit of , forth. if understand issue correctly, doing import when import done want user able select gets saved import?

if not correct, please fix assumptions , update answer.

if correct can is:

  1. change background object creation 

    nsentitydescription *myentity = ... //entity context [[nsmanagedobject alloc] initwithentity:myentity          insertintomanagedobjectcontext:nil];
  2. store these entities in array.
  3. pass entities main thread needed.
  4. release on objects don't want keep
  5. call [mymaincontext insertobject:managedobject] on want keep.
  6. perform save on nsmanagedobjectcontext.

since these entities not part of nsmanagedobjectcontext yet exist in memory , should thread safe since not yet tied down nsmanagedobjectcontext.

this of course theoretical , require testing. should accomplish goal.


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