Thanks for the suggestion Alex. I’m not sure making attributes transient would work though, because the objects themselves would still be persisted, you can still save the context and fetch them back, only that they don’t contain any attributes, if I’m not wrong.
By refreshing the object graph, do you mean updating managed objects instead of deleting and creating? I thought about that, but it seems something quite difficult to do, because I have to compare the json with the graph and figure out what should be created/deleted/updated, and it still requires me to create the graph from scratch when the store is empty. That’s why I’m looking for ways to have a clean sheet before importing json, so I only have one way to manage the object graph (tear down and create from scratch). > On 21 Mar 2018, at 9:27 PM, Alex Finkel <finkel.a...@gmail.com> wrote: > > if you dont want to persist anything, why not make all the attributes > transient? But I would still persist, and just refresh the object graph with > the response based on how often the data may change. > > On Wed, Mar 21, 2018 at 4:56 AM, Glen Huang <hey...@gmail.com > <mailto:hey...@gmail.com>> wrote: > Hi, > > I'm using Core Data as my model, but I don't want to actually persist > anything. Anytime a view controller is shown, I load json data from my server > and populate the store. > > The problem is that objects in Core Data persist between view controllers, > even with in-memory store type. But when I load json data, I’d like to have a > fresh start. So it seems I need to remove existing objects first. > > You might say I shouldn't use Core Data in this case, just use vanilla > objects. But Core Data solves lots of problems, like no need to worry about > memory leak for circular dependencies (my model is pretty complex, lots of > many-to-many relationships etc), NSFetchedResultsController, etc. And with > vanilla objects, when you have a many-to-many relationship, it’s seems it’s > impossible to prevent memory leak: > > class Club { > var people: [Person] > } > class Person { > var name: String > var clubs: [Club] > } > > Array in swift always create strong reference if I’m not wrong, and the two > arrays can create circular references. > > If I go with Core Data, to easily delete objects and have a fresh start, one > solution involves carefully setting up delete rule between object models and > then deleting ones at the level I want, and hope it could cascade throughout, > but the problem is that this approach is very error prone. If I misconfigure > some delete rules, there won’t be any errors, still leaving some objects in > the store. > > I wonder what’s the best way to create object graph in swift without the risk > of leaking memory, if Core Data is the way to go, is there any better way to > easily detect objects that I forgot to delete? Or is there a better way that > I can guarantee that the store is clean before importing json data? > > Best, > Glen > _______________________________________________ > > Cocoa-dev mailing list (Cocoa-dev@lists.apple.com > <mailto:Cocoa-dev@lists.apple.com>) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > <http://lists.apple.com/> > > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/cocoa-dev/finkel.alex%40gmail.com > <https://lists.apple.com/mailman/options/cocoa-dev/finkel.alex%40gmail.com> > > This email sent to finkel.a...@gmail.com <mailto:finkel.a...@gmail.com> > _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
