SwiftUI + OSlog breaks previews in Swift 6

Question

Created 3d

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 import SwiftUI
import OsLog
 
let logger = Logger(subsystem: "Test", category: "Test")
 
struct ContentView: View {
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundStyle(.tint)
            Text("Hello, world!")
        }
        .padding()
        .task {
            logger.info("Hallo")
        }
    }
}
 
#Preview {
    ContentView()
}

     27 |         .padding()
    28 |         .task {
    29 |             logger.info(__designTimeString("#6734_2", fallback: "Hallo"))
       |                         `- error: argument must be a string interpolation
    30 |         }
    31 |     }

Should OsLog be compatible with __designTimeString?

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Answer 1

DTS Engineer OP

Apple

15h

Can you post more info about how you reproduced this?

For context, I tried this here in my office and didn’t encounter a problem. Specifically:

Using Xcode 16.2 on macOS 15.3.2, I created a new project from the Multiplatform > App template.
I replaced ContentView.swift with the code you posted.
I changed OsLog (which looks like a typo for the OSLog framework) to os.log, which is the correct way to import Logger.
I selected My Mac as the run destination.
I resumed the preview and everything looked fine.

my Mac

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—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

0

	import SwiftUI
	import OsLog

	let logger = Logger(subsystem: "Test", category: "Test")

	struct ContentView: View {
	var body: some View {
	VStack {
	Image(systemName: "globe")
	.imageScale(.large)
	.foregroundStyle(.tint)
	Text("Hello, world!")
	}
	.padding()
	.task {
	logger.info("Hallo")
	}
	}
	}

	#Preview {
	ContentView()
	}

	27 \| .padding()
	28 \| .task {
	29 \| logger.info(__designTimeString("#6734_2", fallback: "Hallo"))
	\| `- error: argument must be a string interpolation
	30 \| }
	31 \| }