The Accounts framework provides access to user accounts stored in the Accounts database. An account stores the login credentials of a particular service, such as Twitter, that can be used as authentication for the service. By implementing the Accounts framework into your app, you do not need to be responsible for storing account logins yourself. Instead, the user can grant access for your app to use their account login credentials, bypassing the need to type their username and password. If no account for a particular service exists in the user’s Accounts database, you can let them create and save an account from within your app.

The Address Book framework provides access to a centralized contacts database, called the Address Book database, that stores a user’s contacts. Applications such as Mail and Messages use this database to present information about known and unknown persons.

The Address Book UI framework provides controllers that facilitate displaying, editing, selecting, and creating records in the Address Book database.

A utility that reminds your iPhone app's users to review the app.

Easy to use CFNetwork wrapper for HTTP requests, Objective-C, Mac OS X and iPhone.

In iOS and OS X, the Photos framework (formerly known as Assets Library framework) provides classes that support building photo editing extensions for the Photos app. In iOS, the Photos framework also provides direct access to the photo and video assets managed by the Photos app, including the iCloud Photo Library. Use this framework to retrieve assets for display and playback, edit their image or video content, or work with collections of assets such as albums, moments, and iCloud Shared Albums.

The AV Foundation framework provides an Objective-C interface for managing and playing audio-visual media in iOS and OS X applications.

Bolts is a collection of low-level libraries designed to make developing mobile apps easier.

Cocos2d-x is a cross-platform C++ port of the Cocos2D library. A suite of open-source, cross-platform, game-development tools used by thousands of developers all over the world.

The Contacts framework provides Swift and Objective-C API to access the user’s contact information. Because most apps read contact information without making any changes, this framework is optimized for thread-safe, read-only usage.