Enabling StructuredQueriesCasePaths trait for enum tables

[benblakely]

I’m trying to use enum tables, a.k.a single-table inheritance as described in this blog post:

https://www.pointfree.co/blog/posts/186-new-in-sqlitedata-column-groups-and-inheritance

The post says it’s important to enable the StructuredQueriesCasePaths trait. Does anyone know how to do that?

Things I’ve tried and noticed:

1. The readme for swift-structured-queries shows how to update Package.swift to enable the StructuredQueriesCasePaths trait (and another trait, StructuredQueriesTagged). But I’m not sure if that’s possible in an app built in Xcode using its package management system. And I don’t know if it can be done in a hierarchy where my app depends on sqlite-data which depends on swift-structured-queries.
2. I thought setting a Swift complier flag in my app maybe could enable a trait but I didn’t get anything working there.
3. The Package.swift file for sqlite-data seems to be setup to enable the StructuredQueriesTagged trait as an option (if I’m understanding it correctly) but not for StructuredQueriesCasePaths.
4. I tried forking sqlite-data and changing the Package.swift file to include StructuredQueriesCasePaths in the traits for swift-structured-queries but that didn’t make a difference until I deleted the [email protected] file from my fork of sqlite-data. Then all seemed to work in my app but I assume there’s a better way that I’m missing.

[mbrandonw]

1. But I’m not sure if that’s possible in an app built in Xcode using its package management system.

Hi @benblakely, this is just a current limitation with Xcode. You simply cannot configure traits in Xcode. Hopefully someday soon they will fix it.

But until then you can get around this by adding an SPM package to your project and then in that package you are free to use traits.

[benblakely]

Thanks! That worked.

For anyone else stuck on this, here’s what worked for me:

1. In Xcode, File > Package… I left Multiplatform selected and Library selected. I added it directly to my project’s directory.
2. In my target’s General tab > Frameworks, Libraries, and Embedded Content, I selected the new library.
3. I updated the library’s Package.swift file to the following:

// swift-tools-version: 6.2

import PackageDescription

let package = Package(
    name: "MyLibrary",
    platforms: [
      .iOS(.v13),
      .macOS(.v10_15),
      .tvOS(.v13),
      .watchOS(.v7),
    ],
    products: [
        .library(
            name: "MyLibrary",
            targets: ["MyLibrary"]
        ),
    ],
    dependencies: [
        .package(url: "https://github.com/pointfreeco/swift-case-paths", from: "1.7.2"),
        .package(
            url: "https://github.com/pointfreeco/swift-structured-queries",
            from: "0.22.0",
            traits: ["StructuredQueriesCasePaths"]
        ),
    ],
    targets: [
        .target(
            name: "MyLibrary",
            dependencies: [
                .product(name: "CasePaths", package: "swift-case-paths"),
                .product(name: "StructuredQueries", package: "swift-structured-queries"),
            ]
        ),
    ]
)

I was still getting compiler errors like:

'@Table' can only be applied to enum types when the 'StructuredQueriesCasePaths' package trait is enabled (from macro 'Selection')

But after some combination of restarting Xcode and Product > Clean Build Folder it eventually built successfully. That is, I was able to use an enum like what is shown in the blog post:

@Table struct Attachment {
  let id: Int
  let kind: Kind

  @CasePathable @Selection
  enum Kind {
    case link(URL)
    case note(String)
    case image(URL)
  }
}