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Objective-C iOS Development for Legacy & Enterprise Apps · 课时

使用 NSUserDefaults 存储偏好设置

在 Objective-C 应用中使用 NSUserDefaults 持久化存储轻量级设置和用户偏好；它是 iOS 上最简单的键值存储。

使用 NSUserDefaults 存储偏好设置 是 CoddyKit 上的免费 Objective-C iOS Development for Legacy & Enterprise Apps 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Objective-C iOS Development for Legacy & Enterprise Apps 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Objective-C iOS Development for Legacy & Enterprise Apps 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

What is NSUserDefaults?

NSUserDefaults is a built-in key-value store for small pieces of data — settings, flags, and preferences. It persists automatically across app launches.

When to Use It

Use it for small, simple values:

  • User toggles (dark mode on/off)
  • Last selected tab
  • Onboarding-completed flag

Do NOT use it for large data or sensitive secrets.

The Standard Instance

Access the shared store through standardUserDefaults.

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

Writing Values

Set values by key with typed setters.

[defaults setBool:YES forKey:@"darkMode"];
[defaults setInteger:5 forKey:@"launchCount"];
[defaults setObject:@"Ada" forKey:@"username"];

Reading Values

Read with matching getters. Missing keys return sensible defaults (NO, 0, nil).

BOOL dark = [defaults boolForKey:@"darkMode"];
NSInteger count = [defaults integerForKey:@"launchCount"];
NSString *name = [defaults stringForKey:@"username"];

Supported Types

NSUserDefaults stores property-list types only:

  • NSString, NSNumber, BOOL, integers, doubles
  • NSArray, NSDictionary (of plist types)
  • NSData, NSDate

Persistence is Automatic

Modern iOS writes changes to disk automatically. The old synchronize call is no longer needed and is deprecated.

// [defaults synchronize]; // no longer required

Registering Default Values

Provide fallback values for first launch with registerDefaults:. These apply only until the user changes them.

[defaults registerDefaults:@{@"darkMode": @NO, @"fontSize": @14}];

Removing a Value

Delete a stored key when it is no longer needed.

[defaults removeObjectForKey:@"username"];

Storing Custom Objects

To store a custom object, archive it to NSData first (it must conform to NSCoding), then save that data. NSUserDefaults cannot hold arbitrary objects directly.

Security Caveat

NSUserDefaults is not encrypted. Never store passwords, tokens, or other secrets there — use the Keychain for sensitive data.

Quick Check

Test your NSUserDefaults knowledge.

Recap

You learned NSUserDefaults persistence:

  • A simple key-value store for small preferences
  • Write with setBool:/setObject:, read with matching getters
  • Stores only property-list types
  • Persistence is automatic; synchronize is deprecated
  • Not encrypted — keep secrets in the Keychain

It is the go-to for lightweight settings.

常见问题解答

「使用 NSUserDefaults 存储偏好设置」课时是免费的吗？

是的 — 「使用 NSUserDefaults 存储偏好设置」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Objective-C iOS Development for Legacy & Enterprise Apps 课程的其余内容，请升级到 CoddyKit PRO。 Objective-C iOS Development for Legacy & Enterprise Apps 课程共包含 4 节课。

「使用 NSUserDefaults 存储偏好设置」这节课中我会学到什么？

在 Objective-C 应用中使用 NSUserDefaults 持久化存储轻量级设置和用户偏好；它是 iOS 上最简单的键值存储。 你通过在浏览器中直接运行的动手代码来练习 Objective-C iOS Development for Legacy & Enterprise Apps，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Objective-C iOS Development for Legacy & Enterprise Apps 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Objective-C iOS Development for Legacy & Enterprise Apps 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。

「使用 NSUserDefaults 存储偏好设置」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Objective-C iOS Development for Legacy & Enterprise Apps 课中编写并运行代码吗？

能。每节 Objective-C iOS Development for Legacy & Enterprise Apps 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

  1. 属性列表与归档
  2. Core Data 基础
  3. 使用 FMDB 集成 SQLite
  4. 使用 NSUserDefaults 存储偏好设置
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