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This video covers how to save data using use default sin iOS

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In iOS, the Foundation framework provides the low-level mechanism for storing the preference data. Apps then have two options for presenting preferences:

Display preferences inside the app.

Use a Settings bundle to manage preferences from the Settings app.

Which option you choose depends on how you expect users to interact with preferences. The Settings bundle is generally the preferred mechanism for displaying preferences. However, games and other apps that contain configuration options or other frequently accessed preferences might want to present them inside the app instead. Regardless of how you present them, you use the NSUserDefaults class to access preference values from your code.

This chapter focuses on the creation of a Settings bundle for your app. A Settings bundle contains files that describe the structure and presentation style of your preferences. The Settings app uses this information to create an entry for your app and to display your custom preference pages.

For guidelines on how to manage and present settings and configuration options, see iOS Human Interface Guidelines.

The Settings app implements a hierarchical set of pages for navigating app preferences. The main page of the Settings app lists the system and third-party apps whose preferences can be customized. Selecting a third-party app takes the user to the preferences for that app.

Every app with a Settings bundle has at least one page of preferences, referred to as the main page. If your app has only a few preferences, the main page may be the only one you need. If the number of preferences gets too large to fit on the main page, however, you can create child pages that link off the main page or other child pages. There is no specific limit to the number of child pages you can create, but you should strive to keep your preferences as simple and easy to navigate as possible.

The contents of each page consists of one or more controls that you configure. Table 4-1 lists the types of controls supported by the Settings app and describes how you might use each type. The table also lists the raw key name stored in the configuration files of your Settings bundle.

The Settings Bundle

A Settings bundle has the name Settings.bundle and resides in the top-level directory of your app’s bundle. This bundle contains one or more Settings page files that describe the individual pages of preferences. It may also include other support files needed to display your preferences, such as images or localized strings. Table 4-2 lists the contents of a typical Settings bundle.

In addition to the Settings bundle, the app bundle can contain a custom icon for your app settings. The Settings app displays the icon you provide next to the entry for your app preferences. For information about app icons and how you specify them, see App Programming Guide for iOS.

When the Settings app launches, it checks each custom app for the presence of a Settings bundle. For each custom bundle it finds, it loads that bundle and displays the corresponding app’s name and icon in the Settings main page. When the user taps the row belonging to your app, Settings loads the Root.plist Settings page file for your Settings bundle and uses that file to build your app’s main page of preferences.

In addition to loading your bundle’s Root.plist Settings page file, the Settings app also loads any language-specific resources for that file, as needed. Each Settings page file can have an associated .strings file containing localized values for any user-visible strings. As it prepares your preferences for display, the Settings app looks for string resources in the user’s preferred language and substitutes them in your preferences page prior to display.