Classes

The RequestReceipt is an object vended by the ImageDownloader when starting a download request. It can be used to cancel active requests running on the ImageDownloader session. As a general rule, image download requests should be cancelled using the RequestReceipt instead of calling cancel directly on the request itself. The ImageDownloader is optimized to handle duplicate request scenarios as well as pending versus active downloads.

The ImageDownloader class is responsible for downloading images in parallel on a prioritized queue. Incoming downloads are added to the front or back of the queue depending on the download prioritization. Each downloaded image is cached in the underlying NSURLCache as well as the in-memory image cache that supports image filters. By default, any download request with a cached image equivalent in the image cache will automatically be served the cached image representation. Additional advanced features include supporting multiple image filters and completion handlers for a single request.

The AutoPurgingImageCache in an in-memory image cache used to store images up to a given memory capacity. When the memory capacity is reached, the image cache is sorted by last access date, then the oldest image is continuously purged until the preferred memory usage after purge is met. Each time an image is accessed through the cache, the internal access date of the image is updated.