LRUCache

Objective-C Implementation of the LRU Cache. http://en.wikipedia.org/wiki/Cache_algorithms

Description

Provide easy access to the most recently used objects by key (used NSDictionary and Linked List inside).

Automatically remove least recently used objects if the cache is out of space.

Thread-safe

Append and receive elements from cache is thread-safe (used dispatch_queue inside).

Complexity

Getting an element: O(1)

Adding an element: O(1)

Sample of usage

// initial state of cache with capacity 3
//      -,-,-
LRUCache *cache = [[LRUCache alloc] initWithCapacity:3];

// add 1
//      1,-,-
[cache setObject:@"1" forKey:@"1"];

// add 2
//      2,1,-
[cache setObject:@"2" forKey:@"2"];

// add 3
//      3,2,1
[cache setObject:@"3" forKey:@"3"];

// add 4
//      4,3,2       (1 removed as least recently used)
[cache setObject:@"4" forKey:@"4"];

// request 2
//      2,4,3       (2 goes to the top as most recently used)
NSLog(@"%@", [cache objectForKey:@"2"]);

// add 5
//      5,2,4       (3 removed as least recently used)
[cache setObject:@"5" forKey:@"5"];

NSCoding

Supports NSCoding protocol, so the cache can be archived/unarchived with all stored values (which also should support NSCoding protocol in that way).