我创建了一个项目，该项目从settings.bundle中设置和检索值。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作为
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值，则可以正确检索值。
帮助我完成
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null。默认设置是值的另一个属性。但这并不意味着会将默认值写入默认值。
我所做的是，首先，检查某个设置（我相信它应该有一个值）上是否存储了任何内容。如果它没有任何内容，那么我会编写所有默认值。
下面是一个例子。
在AppDelegate.m上，我检查email_notificaciones_preference是否有值，如果没有，我会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编写默认值的函数。
#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];
}
希望能有所帮助。
如果有人需要，我把答案从MIQUEL翻译成Swift（尽我所能，因为我还在学习）：
var standardUserDefaults = NSUserDefaults.standardUserDefaults()
var us: AnyObject? = standardUserDefaults.objectForKey("your_preference")
if us==nil {
self.registerDefaultsFromSettingsBundle();
}
函数寄存器Default FromSettingsBundle：
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");
}
}
您可以使用这样一个简单的属性包装器：
用法
@SettingsBundleStorage(key: "storageUsage_preference")
var storageUsage: Double
注意这是100%objective-c兼容的，只需在变量之前添加@objc
这背后的代码实现：
设置捆绑包值位于UserDefaults中，因此您可以为其使用自定义PropertyWrapper。以下包装将适用于任何UserDefault值，包括SettingsBundle的所有值。
属性包装器
@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) }
}
}
根和孩子
您应该为根和子plist 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
}
}
}
如果需要，查找并设置默认值
该包装器使用以下函数查找捆绑密钥的默认值：
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文件存储到用户默认值中/从用户默认值恢复，包括所有已经符合可编码文件的Swift标准数据类型。
此外，您可以找到一个类似但代码更少的版本，用于从任何用户默认值访问任何键值，您可以在这里查看这个答案
尝试这个
注册设置捆绑包的默认值
NSDictionary *appDefaults = [NSDictionary dictionaryWithObject:defaultValue forKey:@"key"];
[[NSUserDefaults standardUserDefaults] registerDefaults:appDefaults];
在检索设置捆绑包值之前同步数据
[[NSUserDefaults standardUserDefaults] synchronize]