how to build photo extension in iOS?

To build a photo extension in iOS, you can leverage the new locked camera capture extension introduced in iOS 18. Here are the key steps and considerations based on the session "Build a great Lock Screen camera capture experience" from WWDC 2024:

1. Introduction to Locked Camera Capture Extension:

   • The locked camera capture extension allows you to build a capture experience that runs from the lock screen, enabling users to quickly snap photos or record videos without unlocking their device.
   • This extension can be launched from the control center, the action button, or directly from the lock screen.

2. Lifecycle of a Capture Extension:

   • The extension is a separate target embedded in your application, extending custom functionality and content beyond your app.
   • Once launched, the extension uses the same familiar UI from your app for capturing photos and videos.
   • The extension can either add photo and video assets directly to the user's photo library or store data in a provided directory on the file system.

3. Handling Permissions and Restrictions:

   • The extension inherits camera and photo permissions from your application.
   • It must handle any level of permissions for both camera and photos.
   • The extension is restricted from using network resources and cannot access shared group containers or shared preferences.

4. Using Photokit:

   • Photokit is recommended for saving photo and video assets captured from the extension.
   • It allows adding captured photos and videos to the photo library even when the device is locked.
   • Photokit supports granular levels of photo library access, such as write-only access and limited library support.

5. Persisting Data:

   • On launch, the extension is provided a content path via the session object.
   • Captured content should be written to the provided session content directory.
   • Once the extension is dismissed, the session content directory is migrated to your application's container, and the extension's container is erased.

6. Building the Extension:

   • Xcode provides a template for the locked camera capture extension, which includes a camera, viewfinder, and shutter button.
   • Define your extension to conform to the locked camera capture extension and implement the extension scene for the body to return your custom view content.

For a detailed walkthrough, you can refer to the session "Build a great Lock Screen camera capture experience" from WWDC 2024. Here are some relevant timestamps:

• Introduction
• Lifecycle of a capture extension
• Running on a locked device
• Capturing from the Lock Screen

These sections will provide you with a comprehensive understanding of how to build and integrate a photo extension in iOS.