Re: Creating object graph in swift, Core Data or vanilla objects?
Re: Creating object graph in swift, Core Data or vanilla objects?
- Subject: Re: Creating object graph in swift, Core Data or vanilla objects?
- From: Keary Suska <email@hidden>
- Date: Wed, 21 Mar 2018 11:06:31 -0600
In that case the only way to avoid having to remove objects first, that I can
think of, is to create your own custom persistent store. It’s not too hard, and
might be a better solution in the long run anyway.
Keary Suska
Esoteritech, Inc.
"Demystifying technology for your home or business"
> On Mar 21, 2018, at 9:52 AM, Glen Huang <email@hidden> wrote:
>
> Thanks for the suggestion Keary, but some view controllers only load portion
> of the whole graph.
>
> For example, in the home screen, I show a list of clubs, and when a user taps
> a club, I show its members. Showing members shouldn’t wipe out the whole
> graph, but I do would like to make sure its members are empty before I import
> its member json.
>
>> On 21 Mar 2018, at 11:46 PM, Keary Suska <email@hidden> wrote:
>>
>> Why not just use a different persistent store instance each time? An
>> in-memory store shouldn’t be terribly expensive to create, and you can
>> either keep or dispose of other stores as you need.
>>
>> Keary Suska
>> Esoteritech, Inc.
>> "Demystifying technology for your home or business"
>>
>>> On Mar 21, 2018, at 7:40 AM, Glen Huang <email@hidden> wrote:
>>>
>>> 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 <email@hidden> 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
>>>> <email@hidden<mailto:email@hidden>> 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
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