我创建了一个从settings.bundle设置和检索值的项目。我还在settings.bundle文件中设置了一些默认值。现在的问题是当我检索值时
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
loginName.text = [defaults objectForKey:@"login_name"];
它第一次显示为 null，但这些值是在 iPhone 应用程序设置中设置的。如果我更改值或手动设置它，则可以正确检索值。
帮帮我
尽管您定义了默认设置，但它们并没有真正存储为值。它们被存储为默认值。如果您尝试读取它，则该值为空。默认设置与值一样是另一个属性。但这并不意味着将默认值写入默认值。
我要做的是，首先，检查某个设置（我确定应该有一个值）是否存储了任何内容。如果它没有任何东西，那么我写下所有的默认值。
这是一个例子。
在 AppDelegate.m 上，我检查email_notificaciones_preference是否有值，如果没有，我将所有默认设置写入每个设置。
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
NSUserDefaults * standardUserDefaults = [NSUserDefaults standardUserDefaults];
NSString * email_notificaciones_preference = [standardUserDefaults objectForKey:@"email_notificaciones_preference"];
if (!email_notificaciones_preference) {
[self registerDefaultsFromSettingsBundle];
}
}
这个函数是我用来为每个元素写入默认值的。
#pragma NSUserDefaults
- (void)registerDefaultsFromSettingsBundle {
// this function writes default settings as settings
NSString *settingsBundle = [[NSBundle mainBundle] pathForResource:@"Settings" ofType:@"bundle"];
if(!settingsBundle) {
NSLog(@"Could not find Settings.bundle");
return;
}
NSDictionary *settings = [NSDictionary dictionaryWithContentsOfFile:[settingsBundle stringByAppendingPathComponent:@"Root.plist"]];
NSArray *preferences = [settings objectForKey:@"PreferenceSpecifiers"];
NSMutableDictionary *defaultsToRegister = [[NSMutableDictionary alloc] initWithCapacity:[preferences count]];
for(NSDictionary *prefSpecification in preferences) {
NSString *key = [prefSpecification objectForKey:@"Key"];
if(key) {
[defaultsToRegister setObject:[prefSpecification objectForKey:@"DefaultValue"] forKey:key];
NSLog(@"writing as default %@ to the key %@",[prefSpecification objectForKey:@"DefaultValue"],key);
}
}
[[NSUserDefaults standardUserDefaults] registerDefaults:defaultsToRegister];
}
希望有帮助。
如果有人需要它-我将答案从 MIQUEL 翻译成 Swift（尽我所能，因为我仍在学习）：
var standardUserDefaults = NSUserDefaults.standardUserDefaults()
var us: AnyObject? = standardUserDefaults.objectForKey("your_preference")
if us==nil {
self.registerDefaultsFromSettingsBundle();
}
和函数 registerDefaultsFromSettingsBundle：
func registerDefaultsFromSettingsBundle() {
// this function writes default settings as settings
var settingsBundle = NSBundle.mainBundle().pathForResource("Settings", ofType: "bundle")
if settingsBundle == nil {
NSLog("Could not find Settings.bundle");
return
}
var settings = NSDictionary(contentsOfFile:settingsBundle!.stringByAppendingPathComponent("Root.plist"))!
var preferences: [NSDictionary] = settings.objectForKey("PreferenceSpecifiers") as [NSDictionary];
var defaultsToRegister = NSMutableDictionary(capacity:(preferences.count));
for prefSpecification:NSDictionary in preferences {
var key: NSCopying? = prefSpecification.objectForKey("Key") as NSCopying?
if key != nil {
defaultsToRegister.setObject(prefSpecification.objectForKey("DefaultValue")!, forKey: key!)
}
}
NSUserDefaults.standardUserDefaults().registerDefaults(defaultsToRegister);
}
为 Swift 3 更新：
func registerDefaultsFromSettingsBundle() {
let userDefaults = UserDefaults.standard
if let settingsURL = Bundle.main.url(forResource: "Root", withExtension: "plist", subdirectory: "Settings.bundle"),
let settings = NSDictionary(contentsOf: settingsURL),
let preferences = settings["PreferenceSpecifiers"] as? [NSDictionary] {
var defaultsToRegister = [String: AnyObject]()
for prefSpecification in preferences {
if let key = prefSpecification["Key"] as? String,
let value = prefSpecification["DefaultValue"] {
defaultsToRegister[key] = value as AnyObject
debugPrint("registerDefaultsFromSettingsBundle: (\(key), \(value)) \(type(of: value))")
}
}
userDefaults.register(defaults: defaultsToRegister)
} else {
debugPrint("registerDefaultsFromSettingsBundle: Could not find Settings.bundle")
}
}
swift 2.1 的更新版本：
func registerDefaultsFromSettingsBundle() {
let userDefaults = NSUserDefaults.standardUserDefaults()
if let settingsURL = NSBundle.mainBundle().URLForResource("Root", withExtension: "plist", subdirectory: "Settings.bundle"),
settings = NSDictionary(contentsOfURL: settingsURL),
preferences = settings["PreferenceSpecifiers"] as? [NSDictionary] {
var defaultsToRegister = [String: AnyObject]()
for prefSpecification in preferences {
if let key = prefSpecification["Key"] as? String,
value = prefSpecification["DefaultValue"] {
defaultsToRegister[key] = value
NSLog("registerDefaultsFromSettingsBundle: (\(key), \(value)) \(value.dynamicType)")
}
}
userDefaults.registerDefaults(defaultsToRegister);
} else {
NSLog("registerDefaultsFromSettingsBundle: Could not find Settings.bundle");
}
}
您可以像这样使用简单的属性包装器：
@SettingsBundleStorage(key: "storageUsage_preference")
var storageUsage: Double
请注意，@objc只需在变量之前添加即可 100% 兼容 Objective-c 。
设置捆绑包值是实时的，UserDefaults因此您可以PropertyWrapper为其使用自定义。以下包装器适用于任何UserDefault值，包括SettingsBundle.
@propertyWrapper
public struct SettingsBundleStorage<T> {
private let key: String
public init(key: String) {
self.key = key
setBundleDefaults(plist: .root) // This is the main plist
setBundleDefaults(plist: .child(name: "DeveloperOptions")) // This is an example child.
}
public var wrappedValue: T {
get { UserDefaults.standard.value(forKey: key) as! T }
set { UserDefaults.standard.set(newValue, forKey: key) }
}
}
plist您应该为 root 和 child s传递以下枚举：
extension SettingsBundleStorage {
enum PList {
case root
case child(name: String)
var name: String {
var file: String
switch self {
case .root: file = "Root"
case .child(let name): file = name.replacingOccurrences(of: ".plist", with: "")
}
file.append(".plist")
return file
}
}
}
此包装器使用此函数查找捆绑键的默认值：
extension SettingsBundleStorage {
func setBundleDefaults(plist: PList = .root) {
let settingsName = "Settings"
let settingsExtension = "bundle"
let settingsPreferencesItems = "PreferenceSpecifiers"
let settingsPreferenceKey = "Key"
let settingsPreferenceDefaultValue = "DefaultValue"
guard let settingsBundleURL = Bundle.main.url(forResource: settingsName, withExtension: settingsExtension),
let settingsData = try? Data(contentsOf: settingsBundleURL.appendingPathComponent(plist.name)),
let settingsPlist = try? PropertyListSerialization.propertyList(
from: settingsData,
options: [],
format: nil) as? [String: Any],
let settingsPreferences = settingsPlist?[settingsPreferencesItems] as? [[String: Any]] else {
return assertionFailure("Can not get the \(plist.name) from the bundle: \(settingsName)")
}
var defaultsToRegister = [String: Any]()
settingsPreferences.forEach { preference in
if let key = preference[settingsPreferenceKey] as? String {
defaultsToRegister[key] = preference[settingsPreferenceDefaultValue]
}
}
UserDefaults.standard.register(defaults: defaultsToRegister)
}
}
这个包装器可以将任何类型的可编码存储/恢复到用户默认值中/从用户默认值中恢复，包括已经符合可编码的所有 Swift 标准数据类型。
此外，您可以找到一个类似但代码版本更少的用于从任何用户默认访问任何键值的代码版本，您可以在此处查看此答案
试试这个
注册设置包的默认值
NSDictionary *appDefaults = [NSDictionary dictionaryWithObject:defaultValue forKey:@"key"];
[[NSUserDefaults standardUserDefaults] registerDefaults:appDefaults];
在检索设置包值之前同步数据
[[NSUserDefaults standardUserDefaults] synchronize]