ios - Decoupling Core Data -

most apps i've written use core data follow common pattern - model classes inherit nsmanagedobject , created insertion nsmanagedobjectcontext.

since i'm evaluating couple of different persistence options on new side project, i'd love find way separate out core data implementation rest of code. example, might instead use concept of datastore, defined using protocol. requires implementations provide functionality. example getcars, addcar, , deletecar. app shouldn't need know whether getcars fetching core data, realm, local file, etc.

one of immediate problems i've run core data implementation of datastore car added entity data model, can't create car object except via designated initializer, expects context insert into. won't fly, since whole point separate knowledge of nsmanagedobjectcontext etc various view controllers , other classes.

i thinking using other name core data entities (e.g. cdcar) , adding bunch of code mapping to/from cdcar , car. or perhaps making protocol car general use in app, cdcar conform. there more common approach this?

adding parallel entity adds lot of complexity, point it's not clear decoupling net benefit.

what i'd include factory methods on datastore class create instances on demand. instead of non-datastore code creating car directly, it'd call new createcar method on datastore. datastore whatever needs create valid instance , returns result. mean don't need addcar since wouldn't creating instances outside of datastore.