Decodable CoreStoreObject subclass implementation #239

New Issue

2025-12-29T15:27:12+01:00

adam commented

2025-12-29 15:27:12 +01:00

Originally created by @eraydiler on GitHub (Oct 29, 2018).

Hello,

I'm trying to figure out how to implement a CoreStoreObject subclass that also needs to conform to Decodable protocol. What I came up with is the code below.

`
class TestObject: CoreStoreObject, Decodable {
let title = Value.Optional("title", initial: nil)

 private enum CodingKeys: String, CodingKey {
     case title = "title"
 }

 required init(from decoder: Decoder) throws {
     let values = try decoder.container(keyedBy: CodingKeys.self)

     title.value = try values.decodeIfPresent(String.self, forKey: .title)

     super.init(asMeta: ())
 }

 required init(asMeta: Void) {
     super.init(asMeta: ())
 }

 required init(rawObject: NSManagedObject) {
     super.init(asMeta: ())
 }

}
`

However I'm having error;
❗ [CoreStore: Assertion Failure] Value.swift:373 value
↪︎ Attempted to access values from a 'Test' meta object. Meta objects are only used for querying keyPaths and infering types.

I think issue is related to the init(asMeta:...), init(rawObject:...) methods' implementation.
What is the proper way to implement these methods?
Thanks.

Originally created by @eraydiler on GitHub (Oct 29, 2018). Hello, I'm trying to figure out how to implement a CoreStoreObject subclass that also needs to conform to Decodable protocol. What I came up with is the code below. ` class TestObject: CoreStoreObject, Decodable { let title = Value.Optional<String>("title", initial: nil) private enum CodingKeys: String, CodingKey { case title = "title" } required init(from decoder: Decoder) throws { let values = try decoder.container(keyedBy: CodingKeys.self) title.value = try values.decodeIfPresent(String.self, forKey: .title) super.init(asMeta: ()) } required init(asMeta: Void) { super.init(asMeta: ()) } required init(rawObject: NSManagedObject) { super.init(asMeta: ()) } } ` However I'm having error; ❗ [CoreStore: Assertion Failure] Value.swift:373 value ↪︎ Attempted to access values from a 'Test' meta object. Meta objects are only used for querying keyPaths and infering types. I think issue is related to the `init(asMeta:...), init(rawObject:...)` methods' implementation. What is the proper way to implement these methods? Thanks.

adam closed this issue

2025-12-29 15:27:12 +01:00

adam commented

2025-12-29 15:27:13 +01:00

@JohnEstropia commented on GitHub (Oct 30, 2018):

As mentioned somewhere in the discussion in mogenerator's prototype for Codable support, NSManagedObjects generally do not really play well with Encodable because the init(decoder:) needs to be implemented, while NSManagedObject's init(context:) needs an instance of the NSManagedObjectContext where the object will be added. (Basically you can call init(decoder:) many times without side effects, but init(context:) does)

You are hitting the same limitation with CoreStoreObject here, where it needs the context (via the NSManagedObject in init(rawObject:)).

You can borrow the techniques used in the mogenerator proposal above, but at that point I would recommend you to use ImportableUniqueObjects instead as they are much much more simple.

@JohnEstropia commented on GitHub (Oct 30, 2018): As mentioned somewhere in the discussion in [mogenerator's prototype for Codable support](https://github.com/rentzsch/mogenerator/issues/377), `NSManagedObject`s generally do not really play well with `Encodable` because the `init(decoder:)` needs to be implemented, while `NSManagedObject`'s `init(context:)` needs an instance of the `NSManagedObjectContext` where the object will be added. (Basically you can call `init(decoder:)` many times without side effects, but `init(context:)` does) You are hitting the same limitation with `CoreStoreObject` here, where it needs the context (via the `NSManagedObject` in `init(rawObject:)`). You can borrow the techniques used in the mogenerator proposal above, but at that point I would recommend you to use `ImportableUniqueObject`s instead as they are much much more simple.

adam commented

2025-12-29 15:27:14 +01:00

@eraydiler commented on GitHub (Oct 30, 2018):

I solved my issue by creating two different objects. They conform CoreStoreObject and Decodable seperately. Added additional methods to make required mapping between them. Thanks for the information.

@eraydiler commented on GitHub (Oct 30, 2018): I solved my issue by creating two different objects. They conform CoreStoreObject and Decodable seperately. Added additional methods to make required mapping between them. Thanks for the information.

Sign in to join this conversation.

Branches Tags

develop

prototype/swift6

master

prototype/concurrency

minIOS13

prototype/containers

transactionSourceTracking

prototype/swiftui

minIOS11

swift5_3

prototype/propertyWrapperFields

prototype/propertyWrappers

prototype/propertyWrapper

Swift5

throwables

prototype/Swift_4_1

prototype/Swift_4_0

prototype/Swift_3_2

prototype/queryBuilders

temp/develop

corestore4_develop

prototype/mainContextToPSC

master_ios_7_to_9

swift_2_3

gh-pages

_corespotlight-test

1 Participants

Notifications

Due Date

No due date set.

Dependencies

No dependencies set.

Reference: starred/CoreStore#239