Question

I am storing an array in NSCache.(My NSCache name is aesCache)

 #define DEBUG_CACHE 1
 self.aesCache = [[NSCache alloc] init];
 [self.aesCache setDelegate:self];

To save an array in NSCache

        - (void)saveObjects:(NSMutableArray*)savedObj {
            [self saveValue:savedObj key:@"Objects"];
        }

to save it to NSCache.

 - (void)saveValue:(id)value key:(NSString *)key {
#ifdef DEBUG_CACHE
    NSLog(@"#CACHE_MANAGER: SAVE Object");
    NSLog(@"#CACHE_MANAGER: KEY %@", key);
#endif
    if (value && key) {
        [self.aesCache setObject:value forKey:key];
    }
    else {
#ifdef DEBUG_CACHE
        NSLog(@"#CACHE_MANAGER: *** KEY VALUE SEEMS TO BE NIL ***");
#endif
    }

}

To get that array from cache, I use:

- (NSMutableArray*)getObjects {
    array = [self getValue:@"Objects"];
    #ifdef DEBUG_CACHE
         NSLog(@"#CACHE_MANAGER: Getting the 'Objects' from Cache");
   #endif
        if (areas == nil) {
   #ifdef DEBUG_CACHE
         NSLog(@"#CACHE_MANAGER: No Objects cached. ");
    #endif


    }
    return array;
}

I’ll get the array from the cache.But if I Lock the screen and then open it
the cache delegate function

- (void)cache:(NSCache *)cache willEvictObject:(id)obj {
    #ifdef DEBUG_CACHE
        NSLog(@"#CACHE_MANAGER: Going to evict the object");
    #endif
}

fired and I will get empty result.
How can I solve this issue.

Please help me out.

Answer 1

The aim of NSCache is to cache objets, but it can be flushed at any time to preserve memory. If you want a more persistant cache, you should use a dictionary.