52가지 유효한 방법(50) - 캐시를 구축할 때 NSDictionary 대신 NSCache를 선택합니다.

#import "ViewController.h"

@interface ViewController()
@property (nonatomic, strong) NSCache *myCache;
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    
    for (int i =0 ; i< 5; i++) {
        //  
        NSString *str = [NSString stringWithFormat:@"cache - %d", I];
        [self.myCache setObject:str forKey:@(i)];
    }
    for (int i=0 ; i< 5; i++) {
        NSLog(@"%@", [self.myCache objectForKey:@(i)]);
    }
}

-(NSCache *)myCache
{
    if (_myCache == nil) {
        _myCache = [[NSCache alloc] init];
        _myCache.countLimit = 3;
        _myCache.delegate = self;
    }
    return _myCache;
}

#pragma mark- delegate
-(void)cache:(NSCache *)cache willEvictObject:(id)obj
{
    NSLog(@" obj-------------%@", obj);
}
@end

#import "ViewController.h"

@interface ViewController ()
{
    NSCache *_cache;
}
@end

@implementation ViewController

- (instancetype)init
{
    self = [super init];
    if (self) {
        _cache = [[NSCache alloc] init];
        _cache.countLimit = 100;
        _cache.totalCostLimit = 5 * 1024 * 1024;
    }
    return self;
}

- (void)downloadWithURL:(NSURL *)url
{
    NSPurgeableData *cacheData = [_cache objectForKey:url];
    if (cacheData) {
        [cacheData beginContentAccess];
        
        [self useData:cacheData];
        
        [cacheData endContentAccess];
    }else{
        //network init
        //network block -->data
        {
            NSPurgeableData *purgeableData = [[NSPurgeableData alloc] initWithData:data];
            [_cache setObject:purgeableData forKey:url cost:purgeableData.length];
            
            [self useData:cacheData];
            
            [purgeableData endContentAccess];
        }
    }
}

- (void)useData:(NSPurgeableData *)data {}

@end