NSUserDefaults API简单的介绍和使用英文文件

NSUserDefaults API简单的介绍和使用英文文件

大家好,又见面了,我是全栈君,今天给大家准备了Idea注册码。

NSUserDefaults API简单的介绍和使用英文文件

Overview


The NSUserDefaults class provides a programmatic interface for interacting with the defaults system. The defaults system allows an application to customize its behavior to match a user’s preferences. For example, you can allow users to determine what units of measurement your application displays or how often documents are automatically saved. Applications record such preferences by assigning values to a set of parameters in a user’s defaults database. The parameters are referred to as defaults since they’re commonly used to determine an application’s default state at startup or the way it acts by default.

At runtime, you use anNSUserDefaults object to read the defaults that your application uses from a user’s defaults database.NSUserDefaults caches the information to avoid having to open the user’s defaults database each time you need a default value. Thesynchronize method, which is automatically invoked at periodic intervals, keeps the in-memory cache in sync with a user’s defaults database.

The NSUserDefaults class provides convenience methods for accessing common types such as floats, doubles, integers, Booleans, and URLs. A default object must be a property list, that is, an instance of (or for collections a combination of instances of):NSData,NSString, NSNumber, NSDate, NSArray, orNSDictionary. If you want to store any other type of object, you should typically archive it to create an instance ofNSData. For more details, seePreferences and Settings Programming Guide.

Values returned fromNSUserDefaults are immutable, even if you set a mutable object as the value. For example, if you set a mutable string as the value for“MyStringDefault”, the string you later retrieve using stringForKey: will be immutable.

A defaults database is created automatically for each user. TheNSUserDefaults class does not currently support per-host preferences. To do this, you must use the CFPreferences API (seePreferences Utilities Reference). However, NSUserDefaults correctly reads per-host preferences, so you can safely mix CFPreferences code withNSUserDefaults code.

If your application supports managed environments, you can use anNSUserDefaults object to determine which preferences are managed by an administrator for the benefit of the user. Managed environments correspond to computer labs or classrooms where an administrator or teacher may want to configure the systems in a particular way. In these situations, the teacher can establish a set of default preferences and force those preferences on users. If a preference is managed in this manner, applications should prevent users from editing that preference by disabling any appropriate controls.

The NSUserDefaults class is thread-safe.

Tasks

Getting the Shared NSUserDefaults Instance

  • + standardUserDefaults
  • + resetStandardUserDefaults

Initializing an NSUserDefaults Object

Registering Defaults

  • – registerDefaults:

Getting Default Values

  • – arrayForKey:
  • – boolForKey:
  • – dataForKey:
  • – dictionaryForKey:
  • – floatForKey:
  • – integerForKey:
  • – objectForKey:
  • – stringArrayForKey:
  • – stringForKey:
  • – doubleForKey:
  • – URLForKey:

Setting Default Values

  • – setBool:forKey:
  • – setFloat:forKey:
  • – setInteger:forKey:
  • – setObject:forKey:
  • – setDouble:forKey:
  • – setURL:forKey:

Removing Defaults

  • – removeObjectForKey:

Maintaining Persistent Domains

  • – synchronize
  • – persistentDomainForName:
  • – removePersistentDomainForName:
  • – setPersistentDomain:forName:
  • – persistentDomainNamesDeprecated in OS X v10.9

Accessing Managed Environment Keys

  • – objectIsForcedForKey:
  • – objectIsForcedForKey:inDomain:

Managing the Search List

  • – dictionaryRepresentation

Maintaining Volatile Domains

  • – removeVolatileDomainForName:
  • – setVolatileDomain:forName:
  • – volatileDomainForName:
  • – volatileDomainNames

Maintaining Suites

  • – addSuiteNamed:
  • – removeSuiteNamed:


翻译上面NSUserDefaults的API大概意思例如以下:

NSUserDefaults类提供了一个与默认系统进行交互的编程接口。NSUserDefaults对象是用来保存,恢复应用程序相关的偏好设置。配置数据等等

默认系统同意应用程序自己定义它的行为去迎合用户的喜好。你能够在程序执行的时候从用户默认的数据库中读取程序的设置。同一时候NSUserDefaults的缓存避免了在每次读取数据时候都打开用户默认数据库的操作。能够通过调用synchronize方法来使内存中的缓存与用户默认系统进行同步。


NSUserDefaults类提供了很方便的方法来获取经常使用的类型,比如floats,doubles,intergers,Booleans,URLs。所以一个NSUserDefaults的对象必须是属性表,这也就是说我们能够存储NSData,NSString,NSNUmber,NSDate,NSArray,NSDictionary这些实例

假设你想存储其它类型的对象,你要将其归档并创建一个NSData来实现存储。

从NSUserDefaults返回的值是不可改变的。即便是你在存储的时候使用的是可变的值。比如你使用mutable string做为“MyStringDefault”的值。当你做使用stringForKey:方法获取的值。这个值仍然是不可变的。

NSUserDefaults是单例,同一时候也是线程安全的.


方法具体解释

获取公有的NSUserDefaults实例

[plain] 
view plain
copy

  1. + (NSUserDefaults *)standardUserDefaults;  
  2. 单例模式,获取NSUserDefaults的一个实例。默认Key值例如以下:  
  3. AppleLanguages,  
  4. AppleKeyboardsExpanded,  
  5. AppleITunesStoreItemKinds,  
  6. AppleLocale,  
  7. AppleKeyboards,  
  8. NSLanguages,  
  9. NSInterfaceStyle  

[plain] 
view plain
copy

  1. + (void)resetStandardUserDefaults;  

初始化一个NSUserDefaults的对象

[plain] 
view plain
copy

  1. – (id)init;  
  2. – (id)initWithUser:(NSString *)username;  
  3. init是初始化一个公有的defaults对象  
  4. initWithUser是初始化一个针对username的对象  

注冊一个defaults

[plain] 
view plain
copy

  1. – (void)registerDefaults:(NSDictionary *)registrationDictionary;  
  2. 注冊的内容(registrationDictionary里的)不写入磁盘  

获取Defaults的值

[plain] 
view plain
copy

  1. – (NSArray *)arrayForKey:(NSString *)defaultName;  

[plain] 
view plain
copy

  1. – (BOOL)boolForKey:(NSString *)defaultName;  
  2. 返回一个和defaultName关联的bool值,假设不存在defaultName的话返回NO  
[plain] 
view plain
copy

  1. – (NSData *)dataForKey:(NSString *)defaultName  
  2. 返回defaultName所相应的NSData数据,假设defaultName不存在或者返回的数据不是NSData类型的都会返回nil  
  3. 返回的数据是不可变类型的  
[plain] 
view plain
copy

  1. – (NSDictionary *)dictionaryForKey:(NSString *)defaultName  
  2. 同dataForKey  
[plain] 
view plain
copy

  1. – (float)floatForKey:(NSString *)defaultName  
  2. 同dataForKey  
  3. 假设defaultName不存在返回0  
[plain] 
view plain
copy

  1. – (NSInteger)integerForKey:(NSString *)defaultName  
  2. 同floatForKey  
  3. 假设defaultName不存在返回0  
[plain] 
view plain
copy

  1. – (id)objectForKey:(NSString *)defaultName  
  2. 同dataForKey  
[plain] 
view plain
copy

  1. – (NSArray *)stringArrayForKey:(NSString *)defaultName  
  2. 同dataForKey  
  3. 假设defaultName不存在,或者defaultName所相应的不是一个数组,或者数组包括的不是NSString对象都会返回nil  
[plain] 
view plain
copy

  1. – (NSString *)stringForKey:(NSString *)defaultName  
  2. 同dataForKey  
[plain] 
view plain
copy

  1. – (double)doubleForKey:(NSString *)defaultName  
  2. 同floatForKey  
[plain] 
view plain
copy

  1. – (NSURL *)URLForKey:(NSString *)defaultName  
  2. 同dataForKey  
  3. 当调用[NSUserDefaults URLForKey:]时。有下面3种情况:  
  4. 1.假设值是NSData,NSData能够作为[NSKeyedUnarchiver unarchiveObjectWithData:]的參数。假设NSData能够作为NSURL存档就返回一个NSURL。否则返回nil  
  5. 2.假设值是一个文件引用的URL,那么这个文件引用的URL将会被创建,可是它的书签数据不会被解决直到以后使用NSURL实例  
  6. 3.假设值是一个一~开头的字符串,这个字符串将会用[NSString stringByExpandingTildeInPath]扩展,文件将会以NSURL创建  

设置Defaults值

[plain] 
view plain
copy

  1. – setBool:forKey:  
  2. – setFloat:forKey:  
  3. – setInteger:forKey:  
  4. – setDouble:forKey:  
  5.   
  6. – setObject:forKey:  
  7. 对象參数仅仅能是属性列表对象:NSData,NSString,NSNumber,NSDate,NSArray,NSDictionary  
  8. – setURL:forKey:  

移除Defaults值

[plain] 
view plain
copy

  1. – (void)removeObjectForKey:(NSString *)defaultName  

维护持久域

[plain] 
view plain
copy

  1. – (BOOL)synchronize  
  2. 把持久域中的不论什么改变写到磁盘而且更新磁盘上的不论什么没有改动的持久域  
  3. 假设返回YES表明成功保存到磁盘,相反返回NO  
  4. 这种方法是以一定周期间隔自己主动调用的,假设你不想等待自己主动调用就能够调用这种方法来同步。

    (比如。假设你的应用要退出时,或者你想更新磁盘上的defaults即使你没有做不论什么改变)  

[plain] 
view plain
copy

  1. – (NSDictionary *)persistentDomainForName:(NSString *)domainName  
  2. 返回一个特定持久域的键值对  
[plain] 
view plain
copy

  1. – (NSArray *)persistentDomainNames  
  2. 返回当前的持久域的名称  
[plain] 
view plain
copy

  1. – (void)removePersistentDomainForName:(NSString *)domainName  
  2. 移除相应domainName的持久域  
[plain] 
view plain
copy

  1. – (void)setPersistentDomain:(NSDictionary *)domain forName:(NSString *)domainName  
  2. 设置持久域  
  3. domainName  
  4. This value should be equal to your application’s bundle identifier.  

訪问管理的环境值

[plain] 
view plain
copy

  1. – (BOOL)objectIsForcedForKey:(NSString *)key  
  2. – (BOOL)objectIsForcedForKey:(NSString *)key inDomain:(NSString *)domain  

管理搜索列表

[plain] 
view plain
copy

  1. – (NSDictionary *)dictionaryRepresentation  
  2. 返回搜索列表中相应域的全部的键值对  

维护不稳定的域

[plain] 
view plain
copy

  1. – removeVolatileDomainForName:  
  2. – setVolatileDomain:forName:  
  3. – volatileDomainForName:  
  4. – volatileDomainNames  

维护套件

[plain] 
view plain
copy

  1. – (void)addSuiteNamed:(NSString *)suiteName  
  2. 一个套件能够在不同的应用之间使用  
[plain] 
view plain
copy

  1. – (void)removeSuiteNamed:(NSString *)suiteName  
  2. 移除套件  


演示样例代码例如以下:

#pragma mark---------存    //创建 NSUserDefaults 单例    NSUserDefaults * ud = [NSUserDefaults standardUserDefaults];    //把_userNameTextField.text存到  NSUserDefaults 中    [ud setObject:_userNameTextField.text forKey:@"myKey"];    [ud synchronize];#pragma mark---------取    //从 NSUserDefaults 中取出 数据    NSString * value = [ud objectForKey:@"myKey"];    NSLog(@"value = %@",value);


版权声明:本文博主原创文章,博客,未经同意不得转载。

版权声明:本文内容由互联网用户自发贡献,该文观点仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 举报,一经查实,本站将立刻删除。

发布者:全栈程序员-用户IM,转载请注明出处:https://javaforall.cn/117104.html原文链接:https://javaforall.cn

【正版授权,激活自己账号】: Jetbrains全家桶Ide使用,1年售后保障,每天仅需1毛

【官方授权 正版激活】: 官方授权 正版激活 支持Jetbrains家族下所有IDE 使用个人JB账号...

(0)
blank

相关推荐

发表回复

您的电子邮箱地址不会被公开。

关注全栈程序员社区公众号