Simultaneous Accesses to 0X1C0A7F0F8, But Modification Requires Exclusive Access Error on Xcode 9 Beta 4

Simultaneous accesses to 0x6040000155d8, but modification requires exclusive access

You should try updating this line

createGameModel?.createGameOptions?.removeSubrange(2...((createGameModel?.createGameOptions?.count)! - 2))

To

let count = (createGameModel?.createGameOptions?.count)!
createGameModel?.createGameOptions?.removeSubrange(2...(count - 2))

Try and share the results

Simultaneous accesses to 0x14572f2a0, but modification requires exclusive access

This is what you get for testing the code in a playground — there's no debugger! If you try that code in a real app, the debugger tells you exactly what the problem is.

The problem is here:

public func withdraw(amount: Float) -> Bool {
    return state.withdraw(amount: amount) // <-- *
}

The withdraw state's withdraw method sets the state property of its context, which is this ATM instance. So the call to state.withdraw means that we both mutate this ATM's state value directly, by replacing it with a different state object, and call its mutating method withdraw, in a single move. You can't do that, because the double mutation, to a property of the struct and to a reference to the struct as a whole, is incoherent. You have to proceed in stages, like this:

public func withdraw(amount: Float) -> Bool {
    // fetch
    var theState = self.state
    // mutate
    return theState.withdraw(amount: amount)
}

The alternative would be to make all of the state types classes instead of structs. A class, unlike a struct, is mutable in place. That would require considerably more rewriting, however, so that is left as an exercise for the reader.

SwiftUI @AppStroage - 'Simultaneous accesses to *, but modification requires exclusive access'

I am going to attribute this to a SwiftUI bug. I have submitted it to Apple (FB9975464). The issue seemed to be in the CrashSetting initializer, but it actually occurs without it. I believe the issue is using the dot (.) character in the AppStorage key. It has also caused [error] precondition failure: setting value during update: 5848. I haven't been able to produce a small demo with that crash, but removing the "." from my keys also solves it. If you experience any of the above, specifically while transitioning/navigating views, it's worth checking your AppStorage keys.

Simplest Crash Demo

1. Build on iPad mini
2. Tap Back button

import SwiftUI

@main
struct AppStorage_Key_IssueApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

struct ContentView: View {
    // Using the "." character results in many hard to track crashes
    @AppStorage("a.b")
    var val = ""
    
    var body: some View {
        NavigationView {
            PrimaryView()
            Color.blue
        }
    }
}

struct PrimaryView: View {
    var body: some View {
        List {
            NavigationLink {
                Color.red
            } label: {
                Text("crashes")
            }
        }
        .listStyle(InsetGroupedListStyle())
    }
}

Thread 5: Simultaneous accesses to 0x10b883638, but modification requires exclusive access

Try this code:

    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {

    // Only handle observations for the playerItemContext
    guard context == &P2SheetViewController.playerStatusContext else {
        super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
        return
    }

    if keyPath == #keyPath(AVPlayer.status) {
        let status: AVPlayer.Status
        if let statusNumber = change?[.newKey] as? NSNumber {
            status = AVPlayer.Status(rawValue: statusNumber.intValue)!
        } else {
            status = .unknown
        }

        //Switch over status value
        switch status {
        case .readyToPlay:

            break
        // Player item is ready to play
        case .failed:
            print(".UKNOWN")

            break
        // Player item failed. See error.
        case .unknown:
            print(".UKNOWN")

            break
        // Player item is not yet ready.
        @unknown default: //new jul 17
            print(".UKNOWN")

            break
        }

    }
}

Hope it helps

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