Thread 1: Fatal error: expected attribute to be Codable

Question

BenLeggiero_0 OP

Created Jul ’23

Replies 7

Boosts 1

Views 1.8k

Participants 5

Not sure what I'm doing wrong here. I'm taking this opportunity to add persistence to an app that hadn't had it yet.

I followed the session advice but I get this crash when running it:

SwiftData/BackingData.swift:201: Fatal error: expected attribute to be Codable

The crash is on this line:

modelContext.insert(RentSplitDataModel())

The object being created and inserted there is simple and the compiler confirms it does conform to Codable: https://github.com/KyLeggiero/Rent-Split-for-iOS/blob/feature/MVP/Shared/Model/RentSplitDataModel.swift

Answered by BenLeggiero_0 in 762497022

This is caused by the fact that SwiftData does not yet support encoding custom Codable types, despite the claims from Apple. You'll have to make your model only use primitives such as Int, String, Date, etc

Boost

Answer 1

newwbee OP

Jul ’23

Start small .... not sure what MoneySplitter in your code is.

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Answer 2

BenLeggiero_0 OP

Jul ’23

please ignore this accidental reply

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Answer 3

BenLeggiero_0 OP

Jul ’23

@newwbee it's open-source. MoneySplitter is a simple struct with a lot of extension functions and Codable conformance: https://github.com/KyLeggiero/RentSplitTools/blob/765c748ff08e2fd0d4a1c00e8440f7ac3c6d703c/Sources/RentSplitTools/MoneySplitter.swift

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Answer 4

AndyJJ OP

Jul ’23

Couldn't find a place where it says MoneySplitter conforms to Codable.

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Answer 5

BenLeggiero_0 OP

Jul ’23

@AndyJJ whoops; sorry about that. Linked an incorrect commit hash. Here you go: https://github.com/KyLeggiero/RentSplitTools/blob/181316d7a37b4b1615d15f10bb2ff2722fab088b/Sources/RentSplitTools/MoneySplitter.swift#L685

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Answer 6

BenLeggiero_0 OP

Aug ’23

Accepted Answer

This is caused by the fact that SwiftData does not yet support encoding custom Codable types, despite the claims from Apple. You'll have to make your model only use primitives such as Int, String, Date, etc

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Answer 7

ollmann_ph OP

Sep ’23

I had exactly the same error message during runtime. The solution for me was to change from .modelContainer(for: [StoredHabit.self], isAutoSaveEnabled: true, isUndoEnable: true) to .modelContainer(for: [StoredHabit.self]). After that, the error was gone and SwiftData worked properly again.

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