ios - How to get Core Data object from specific Object ID? -

i can object's id in core data using following code:

nsmanagedobjectid *moid = [managedobject objectid]; 

however, there way object out of core data store giving specific object id? know can using nsfetchrequest, this:

nsfetchrequest *fetchrequest = [[nsfetchrequest alloc] init]; nsentitydescription *entity = [nsentitydescription entityforname:@"document" inmanagedobjectcontext:managedobjectcontext]; [fetchrequest setentity:entity];  nspredicate *predicate = [nspredicate predicatewithformat:@"(objectid = %@)", myobjectid]; [fetchrequest setpredicate:predicate]; 

however, i'd in way not initiate own fetch request. ideas?

you want:

-(nsmanagedobject *)existingobjectwithid:(nsmanagedobjectid *)objectid                                    error:(nserror **)error 

fetches object store has id, or nil if doesn't exist.

(be aware: there 2 methods on nsmanagedobjectcontext similar-seeming names tripped me up. keep them straight, here's other 2 do:

-(nsmanagedobject *)objectwithid:(nsmanagedobjectid *)objectid 

...will create fault object provided objectid, whether or not such object exists in store. if doesn't exist, fires fault fail unless insert object first nsmanagedobjectcontext's insertobject:. use i've found copying objects store store while preserving objectids.

-(nsmanagedobject *)objectregisteredforid:(nsmanagedobjectid *)objectid 

...will return object has id, if has been fetched store managedobjectcontext. if knows method useful for, please comment.)

[eta.: important difference between first method , other 2 existingobjectwithid:error: never returns fault; fetches whole object you. if you're trying avoid (e.g. working expensive-to-fetch object big blob property), have clever objectwithid: or objectregisteredforid:, don't fire faults; or use configured fetch request.]