Swift 4.1更新后出现Thread 1: EXC_BAD_ACCESS错误求助

Hey there, let's tackle this crash you're hitting after updating to Swift 4.1. That EXC_BAD_ACCESS error is definitely vague, but based on your code and the context, here are the most likely culprits and how to fix them:

1. Recursive Initialization Loop #

First, check where this code is running. If it's inside a default init() method of your class, and that init() calls self.init(settings: settings), you might be creating an infinite recursion loop. For example:

class YourClass {
    init() {
        // Your problematic code here
        if let settingsData = UserDefaults.standard.data(forKey: "settings"), 
           let settings = try? JSONDecoder().decode(ExploreSettings.self, from: settingsData) {
            self.init(settings: settings) // This calls another init, which might loop back
        }
    }

    init(settings: ExploreSettings) {
        // If this init indirectly calls the default init, boom—recursion crash
    }
}

Fix: Move the UserDefaults loading logic outside the init chain. Use a static factory method instead:

static func loadFromDefaults() -> YourClass {
    if let settingsData = UserDefaults.standard.data(forKey: "settings"), 
       let settings = try? JSONDecoder().decode(ExploreSettings.self, from: settingsData) {
        return YourClass(settings: settings)
    }
    return YourClass(settings: ExploreSettings.defaultSettings) // Fallback to defaults
}

2. Codable Compatibility Issues in ExploreSettings #

Swift 4.1 tightened up some edge cases for the Codable protocol. Even if your code worked before, double-check your ExploreSettings definition:

• If it's a class inheriting from NSObject, make sure all properties marked for decoding are Codable-compliant. Avoid mixing @objc properties with Codable unless you explicitly handle them in CodingKeys.
• If you have a custom init(from decoder: Decoder) implementation, ensure you're not missing any required properties, and that you're properly initializing all stored properties before using self. For classes, don't forget to call super.init() if needed (and make sure it's called at the right time).
• Verify your CodingKeys enum matches exactly with the keys in the stored JSON. Swift 4.1 is stricter about key mismatches that might have been ignored before.

3. Stale UserDefaults Data #

The data stored in UserDefaults might have been encoded with an older Swift version's JSONEncoder, which could have subtle differences in how types (like Date, URL, or nested objects) are serialized.
Fix: Temporarily clear the stored data to test this:

UserDefaults.standard.removeObject(forKey: "settings")

Run your app again. If the crash goes away, you'll need to add migration logic—catch decoding errors and fall back to default settings when old data can't be decoded.

4. Uninitialized Property Access #

If self.init(settings: settings) is trying to access properties that haven't been initialized yet (even indirectly), that can trigger an EXC_BAD_ACCESS error. Double-check the order of initialization in your init(settings:) method—make sure all stored properties are set before any method calls or property accesses that rely on them.

Quick Debugging Step #

Comment out the self.init(settings: settings) line and replace it with a print statement:

if let settingsData = UserDefaults.standard.data(forKey: "settings"), 
   let settings = try? JSONDecoder().decode(ExploreSettings.self, from: settingsData) {
    print("Decoded settings: \(settings)")
    // self.init(settings: settings)
}

If this runs without crashing, the problem is definitely in the initialization chain. If it still crashes, the issue is with decoding ExploreSettings from the stored data.

内容的提问来源于stack exchange，提问作者user3116871