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.

The Firebase iOS framework for adding realtime data synchronization to your app.

Nanopb - protocol buffers with small code size

Work with image and video assets managed by the Photos app, including those from iCloud Photo Library and Live Photos. Fetch and cache full-sized assets or thumbnails asynchronously, revise content, and sync revisions to multiple devices. In iOS and macOS, the Photos framework provides classes that support building photo editing extensions for the Photos app. In iOS and tvOS, 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.

Create view-level services for media playback, complete with user controls, chapter navigation, and support for subtitles and closed captioning.

The Core Motion framework lets your application receive motion data from device hardware and process that data. The framework supports accessing both raw and processed accelerometer data using block-based interfaces. For devices with a built-in gyroscope, you can retrieve the raw gyro data as well as processed data reflecting the attitude and rotation rates of the device. You can use both the accelerometer and gyro-based data for games or other apps that use motion as input or as a way to enhance the overall user experience.

The GLKit framework provides functions and classes that reduce the effort required to create new shader-based apps or to port existing apps that rely on fixed-function vertex or fragment processing provided by earlier versions of OpenGL ES or OpenGL.