緩存下載的數據

Question

我正在使用集合視圖在每個單元格中顯示產品數據。 每次用戶刷新collectionview ，它都會再次從服務器獲取數據。

我需要知道是否有可用的緩存機制來緩存下載的圖像。 我只想下載未緩存的最近更新的產品。

NSURL *url = [NSURL URLWithString:@"http://www.myURL/productAll.php"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
    NSError *myError = nil;
    id res = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:&myError];        
    items = [[NSMutableArray alloc] init];
    for (int i=0; i<[res count]; i++) {
        NSString *arrayResult = [[res objectAtIndex:i]objectForKey:@"image"];            
        NSData *data = [[NSData alloc] initWithBase64EncodedString:arrayResult options:NSDataBase64DecodingIgnoreUnknownCharacters];
        UIImage *captcha_image = [[UIImage alloc] initWithData:data];
        [items addObject:captcha_image];
    }
    [collectionView reloadData];
}];

Answer 1

使用NSURLCache可以如下設置內存和磁盤緩存：

int cacheSizeMemory = xxxxx; //in memory cache
int cacheSizeDisk = xxxxx; //disk cache
NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:cacheSizeMemory diskCapacity:cacheSizeDisk diskPath:@"nsurlcache"];
[NSURLCache setSharedURLCache:sharedCache];