#LRUCache
Your mobile-device’s RAM is limited; and when you hit the limit, you’ll get a memory warning. Failing to release memory when you receive this warning will crash your app.
Purpose: LRUCache enhances data-access by storing frequently-used data in memory (cache) and allowing the cache to purge least-recently-used (LRU) data.
‘MyLRU’ is a proof-of-concept of using LRU (Least Recently Used) cache design pattern. ‘MyLRU’ serializes user-data (NSData) into a NSData object within the in-memory cache layer and archive and unarchive some of the cache’s contents when memory is limiting.
Modus Operandi: A dictionary is used to hold your cached data in memory. There’s a size limit to the memory; so when anything is added to the cache after it’s full, the least-recently used object (least recently used) should be saved to file (flash memory).
This code also handles memory warnings and write the in-memory cache to flash memory (as files). All in-memory cache are written to flash memory (files) when the app is closed or quit or when it enters the background.
Variables:
- A NSMutableDictionary for storing the cache data.
- A NSMutableArray is used to keep track of recently-used items, in chronological order, and an integer that limits the maximum size of this cache.
The @synchronized directives wrap thread-sensitive portions of the code to allow for thread safety.
A Unit-Testing target is provided.