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swiftxcodeswiftuipreviewxcode12

Content Previewer not loading on Xcode 12.5.1

I was working on a project the other day, and my preview stopped working. I got the error "Compiling Failed, cannot find "DataType" in scope" (all code/relationships will be shown below). I have restarted XCode a few times, and even commented out that area of code but it continues to not work, is anyone else having this problem and how can I fix it?

I am previewing a sheet called "Profile Sheet", just a standard swiftUI View, so the preview code looks like:

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ProfileSheet()
    }
}

In the profile sheet, it is accessing data from a static function associated with my model file (different struct, different file), the functions it is using, and the ones that define "DataType", the problematic generic are here:

static func saveData<DataType>(data: DataType, for key: String) {
        defaults.setValue(data, forKey: key)
    }
    
static func retrieveData<DataType>(defaultValue: DataType, for key: String) -> DataType {
        guard let value = defaults.value(forKey: key) as? DataType else {return defaultValue}
        return value
    }
    
static func saveComplexData<DataType>(data: DataType, for key: String) where DataType: Codable {
        let encodedData = try! JSONEncoder().encode(data)
        defaults.setValue(encodedData, forKey: key)
    }

static func retrieveComplexData<DataType>(defaultValue: DataType, for key: String) ->  DataType where DataType: Codable {
        guard let retrievedData = defaults.value(forKey: key) as? Data else { return defaultValue}
        let decodedData = try! JSONDecoder().decode(DataType.self, from: retrievedData)
        return decodedData

    }

all of these function as intended, and obviously compile. Even when I run to launch the previewer and compiles my app does it builder properly, its only when it is then trying to launch the preview simulator.

Finally, I thought Id remove those functions entirely and just try to display a View that has no connection to them, so I previewed Text("test") and got the same error.

on Xcode 13 beta 3 & 4 I am able to run the simulator, but I cannot work only on those betas as they are still fairly unstable.

Any help is appreciated :)

Solution

  • I've seen quite a bit of weird behavior with frameworks, I think due to changes to the simulators to support Apple silicon. My temporary workaround is, in my app/extension targets, to add "arm64" to the Excluded Architectures build setting when building for the simulator (as your preview appears to be trying to do), and setting "Build Active Architecture Only" to No for all schemes. Might be worth a try.

    As per triplette in apple developer answers.

    Try to check it out https://developer.apple.com/forums/thread/657913

    I believe it's not an issue with your code it's an issue with Xcode due to apple silicon macs. try to do a software update and reinstall the Xcode.