![]() The solution consists of making sure that the optional is not nil before force-unwrapping it: let userPref = defaults.stringForKey("userPref")Īn even better way is by using optional binding: if let userPref = defaults. The forced unwrapping operator should be used only when an optional is known to contain a non-nil value. The reason is that the forced unwrapping operator ! is attempting to force unwrap a value from a nil optional. But if the key doesn’t exist, or the corresponding value is not a string, the app crashes with the following error: fatal error: unexpectedly found nil while unwrapping an Optional value Performance may be impacted if you store large amounts of text, as the API was designed to store small amounts of text.The second line uses the stringForKey method of NSUserDefaults, which returns an optional, to account for the key not being found, or for the corresponding value not being convertible to a string.ĭuring its execution, if the key is found and the corresponding value is a string, the above code works correctly. You can disable this by following Google's Auto Backup documentation. This feature is on by default and preserves app data, including Shared Preferences, which is what the Preferences API uses. Uninstalling the application causes all preferences to be removed, except when the app runs on Android 6.0 (API level 23) or later, while using the Auto Backup feature. Each preference value can be up to 8K bytes in size, and each composite setting can be up to 64 K bytes in size. LocalSettings restricts the preference key names to 255 characters or less. Otherwise the name is used to create a new container inside of LocalSettings. If no sharedName is specified, the LocalSettings are used. Otherwise, the name is used to create a new NSUserDefaults with the specified name used for the NSUserDefaultsType.SuiteName.ĪpplicationDataContainer is used to store the values on the device. If no sharedName is specified, the StandardUserDefaults are used. NSUserDefaults is used to store values on iOS devices. Otherwise, the name is used to get a private Shared Preferences with the specified name. If no sharedName is specified, the default Shared Preferences are used. The following methods take a string parameter named sharedName:Īll data is stored into Shared Preferences. So, add this after the tapCount + 1 line: (self.tapCount, forKey: 'Tap') In just that single line of code you can see three things in action: We need to use UserDefaults.standard. When you set, remove, or retrieve a preference, an optional string parameter can be supplied to specify the name of the container the preference is stored in. However, you can also create a shared preference that can be used by other extensions or a watch app. The preferences stored by your app are only visible to your app. To remove all keys, use the Clear method: () Use the Remove method to remove a specific key from preferences: ("first_name") Use the ContainsKey method to determine if a key exists: bool hasKey = ("my_key") So you can't rely on the default value as an indicator that the key doesn't exist. Even though Get has you set a default value when the key doesn't exist, there may be cases where the key existed, but the value of the key matched the default value. ![]() It may be useful to check if a key exists in the preferences or not. Int age = ("age", -1) īool hasPets = ("has_pets", false) To retrieve a value from preferences, you pass the key of the preference, followed by the default value when the key doesn't exist: string firstName = ("first_name", "Unknown") Right now on a fresh app install until a user sets an image into UserDefaults, the app crashed. If UserDefaults is empty and if it is, display an image. Preferences are set by calling the Preferences.Set method, providing the key and value: // Set a string value: I have a single image stored in UserDefaults, but until a user sets it, UserDefaults is empty. See the documentation of these methods for adjustments that might be made to decoded values when a DateTime is stored that isn't a Coordinated Universal Time (UTC) value.
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