SimpleCache.m

SimpleCache.m

// CacheItem.h
@interface CacheItem : RLMObject

@property NSString *key;
@property NSData *value;

@end

// CacheItem.m
@implementation CacheItem

+ (NSString *)primaryKey {
    return @"key";
}

@end

// SimpleCache.h

@interface SimpleCache : NSObject

+ (instancetype)sharedCache;

- (CacheItem *)objectForKey:(NSString *)key;
- (void)saveObject:(CacheItem *)item;
- (void)clear

@end

// SimpleCache.m
@interface SimpleCache ()

@property (nonatomic, strong) RLMRealm *defaultRealm;
@property (nonatomic, strong) NSCache *memCache;

@end

@implementation SimpleCache

+ (instancetype)sharedCache {
    static sharedCache *instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] init];
    });

    return instance;
}

- (instancetype)init {
    self = [super init];
    if (self) {
        _defaultRealm = [RLMRealm defaultRealm];
        _memCache = [[NSCache alloc] init];
    }

    return self;
}

#pragma mark - Persistence
- (CacheItem *)objectForKey:(NSString *)key {
    CacheItem *item = [self.memCache objectForKey:key];
    if (!item) {
        item = [CacheItem objectForPrimaryKey:key];
        if (item) {
            [self.memCache setObject:item forKey:key];
        }
    }

    return item;
}

- (void)saveObject:(CacheItem *)item {
    if (!item.key || !item.value) {
        return;
    }

    [self.defaultRealm transactionWithBlock:^{
        [self.defaultRealm addOrUpdateObject:item];
    }];

    // Save to mem cache after the object is saved to Realm
    [self.memCache setObject:item forKey:item.key];
}

#pragma mark - Clear
- (void)clear {
    [self.memCache removeAllObjects];
    [self.defaultRealm transactionWithBlock:^{
        [self.defaultRealm deleteObjects:[CacheItem allObjects]];
    }];
}

@end