Modify exsiting data model in SwiftData

Question

I need to add a new property to a class modeled in SwiftData after the project has been compiled and some data already been saved to the underlying container. But the app crashed when I tried to build and run the project with the modified data model. For example, the data model is as follows:

import Foundation
import SwiftData

@Model
final class TileView {
    @Attribute (.unique) var tileName
    var tileLegth: Double
    var tileWidth: Double
    var tilePatternName: String
    // var tileType: String // This is later added

   init(tileName: String, tileLength: Double, tileWidth: Double, tilePatternName: Double/*, tileType: String*/) {
       self.tileName = tileName
       self.tileLength = tileLength
       self.tilePatternName = tilePatternName
       // self.tileType = tileType
   }
}

When the commented code in the above code snippet is uncommented after the app has been built and run initially, the app crashes if it is built and run subsequently. Is there a safe way to modify (e.g. add to or remove properties) existing models like the above? Thank you so much.

Or you can give a default value for the new property and SwiftData will do the migration for you. — Joakim Danielson
– Joakim Danielson, Commented Nov 11, 2023 at 7:10

Michael May · Accepted Answer · 2023-11-11 21:52:12Z

-4

Problem solved. It's because I didn't migrate the @Relationship var, so the runtime couldn't find it in the new version of the model. Sorry, I didn't put the @Relationship var in the code snippet I provided in my post because I didn't know it was the missing of the @Relationship var in the initialiser of the new version that had caused the problem.

Thank you for your participation and suggestions.

answered Nov 11, 2023 at 21:52

Michael May

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4 Comments

HangarRash Over a year ago

This would be more helpful if you showed the code both before and after the needed change(s).

Michael May Over a year ago

Thank you, @HangarRash for your kind suggestion. But that would a whole lot of code to paste here. I'm sorry I'm in a hurry to do something else at the moment. I may come up with the code whenever I've got a minute later.

HangarRash Over a year ago

I certainly don’t mean all of your code. Just the relevant changes to your class.

Joakim Danielson Over a year ago

Or maybe it's better you remove the whole question then since it seems to be based on a mistake and isn't that helpful to others.

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