FB12527597: Previews fail to build with linker error when using SwiftData

[insidegui]

• Date: 2023-07-05
• Resolution: Open
• Area: Xcode
• OS: macOS 13.4
• Type: Incorrect/Unexpected Behavior
• Keywords: Xcode, SwiftUI, SwiftData

Details

What version of Xcode are you using? 15.0 beta 3 (15A5195k)

Did you see an error message? Yes

What was the error? ld: Undefined symbols: unsafeMutableAddressor of self

Description

Xcode fails to build a simple iOS app target for previews when it contains models that use SwiftData’s @Model macro.

Steps to reproduce:

• Create an iOS app in Xcode 15 beta 3 with the deployment target set to iOS 17
• Create a new Swift file called “DatabaseModels” or something and add a SwiftData model, like this:

@Model class MySimpleDatabaseModel {
    @Attribute(.unique) var id: String

    init(id: String) { self.id = id }
}

• Build the iOS app target, you’ll notice that it builds successfully
• Select the “ContentView” file that was automatically created as part of the app template
• Reveal the preview canvas and press Command + Option + P to request a preview

Expected results:

The app preview should compile and run successfully.

Actual results:

The app preview fails to compile with the following linker errors:

ld: Undefined symbols:
  unsafeMutableAddressor of self #1 : PreviewCompileBug.MySimpleDatabaseModel in PreviewCompileBug.MySimpleDatabaseModel.id.init : Swift.String, referenced from:
      PreviewCompileBug.MySimpleDatabaseModel.id.init : Swift.String in DatabaseModels.o
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Notes:

• Reproduced running Xcode 15 beta 3 on both macOS 13.4 and macOS 14.0 beta 3
• The issue was initially found when building an iOS app, build the same can be reproduced with a Mac app target as well, or even a framework target
• There’s a sample project attached that reproduces the issue

[davesly]

This seems to be an issue with SwiftData. I was having the same problem, and removing the @Model macro annotation (and associated code) corrected the preview issue. Obviously not ideal, but helps narrow it down.

[ViktorEvil]

can confirm, my app I had converted to SwiftData no longer builds

[insidegui]

Turns out this is listed as a known issue in the Xcode 15 beta 3 release notes:

[ViktorEvil]

Managed to get mine to build (first one took a while), but not being able to use previews is not very convenient at all.

[iJustinCabral]

Can confirm this as well. Can build to simulator and phone with no issue but the preview canvas fails due the @Model macro associated with SwiftData.

[davesly]

Turns out this is listed as a known issue in the Xcode 15 beta 3 release notes:

Good catch! I need to be better in the future about going line-by-line in the release notes. Thanks for pointing this one out!

[Max094Reikeb]

I have the same issue when building the app to place it on my device. Is there a workaround for this to test the app on our devices?

[hcri50]

having the same problem. What is strange is that I erased the Hard Drive and did a fresh install and then a fresh install of Xcode Beta 3 and right away, I am having the same problem. And again, once I remove @Model the problem goes away

Undefined symbols:

Linker command failed with exit code 1 (use -v to see invocation)

[Aparikk]

Same here :( How can such a major bug slip through? Or is there a way to use SwiftData without the @Model macro?

[ViktorEvil]

Same here :( How can such a major bug slip through? Or is there a way to use SwiftData without the @model macro?

You can use SwiftData but you have to comment out the new #Previews which makes is a bit inconvenient

[Aparikk]

Same here :( How can such a major bug slip through? Or is there a way to use SwiftData without the @model macro?

You can use SwiftData but you have to comment out the new #Previews which makes is a bit inconvenient

Ah… I haven’t tried using the old Preview struct. If this still works, it’s only half as bad.

[ViktorEvil]

not fixed on beta 4

[Aparikk]

Yup and the good old PreviewProvider also does not work :<

[Max094Reikeb]

The issue only appears with @model macro when using SwiftData. Even with old PreviewProvider, it does not work. And beta 4 does not fix the issue... (it is still written as a known issue)

[egesucu]

This has been mentioned in the Xcode 14 beta 4 release notes:

• Previewing view code in a SwiftData app results in a linker failure for the canvas despite that code compiling successfully for device and simulator. (111657477) Workaround: Run your app in the simulator to test your UI instead of using Previews.

[Max094Reikeb]

This has been mentioned in the Xcode 14 beta 4 release notes:

• Previewing view code in a SwiftData app results in a linker failure for the canvas despite that code compiling successfully for device and simulator. (111657477) Workaround: Run your app in the simulator to test your UI instead of using Previews.

I tried to run my app on my own iPhone, it still didn't work...

[Aparikk]

This has been mentioned in the Xcode 14 beta 4 release notes:

• Previewing view code in a SwiftData app results in a linker failure for the canvas despite that code compiling successfully for device and simulator. (111657477)

  Workaround: Run your app in the simulator to test your UI instead of using Previews.

I tried to run my app on my own iPhone, it still didn't work...

Must be something different then. For me both simulator and own device do work.

[Max094Reikeb]

Must be something different then. For me both simulator and own device do work.

Could you show me a quick example, with a simple @model class, with a single view?

[ViktorEvil]

Simulator and devices all work for me but the #Preview code must be commented out or previews disabled in the editor otherwise I get the error

[OliveCh12]

I also commented out the function to generate the preview #Preview, the error disappears. However, it's not very convenient to rebuild the project every time, especially when making small changes in the interface. Hopefully, someone will fix this issue soon.

[OliveCh12]

Look's like the problem is solved by installing Xcode 15 beta 5 ✅