iOS NSCache 内存缓存

• NSCache 是内存缓存，可以暂时储存到内存，当程序退出时储存的内容就会消失

-(NSCache *)cache
{
    if (!_cache) {
        _cache = [[NSCache alloc] init];
        _cache.countLimit = 100;
        _cache.totalCostLimit = 5 * 1024 * 1024; // 5M
    }
    return _cache;
}

NSData *cachedData = [_cache objectForKey:@"REQUEST"];
    if (cachedData) {
        NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:cachedData options:kNilOptions error:nil];
        NSLog(@"cachedData -%@",dict);
    } else {
        NSLog(@"暂无缓存");
        __weak typeof(self) weakSelf = self;
        NSURL *url = [NSURL URLWithString:@"https://weatherapi.market.xiaomi.com/wtr-v3/weather/all?latitude=110&longitude=112&isLocated=true&locationKey=weathercn%3A101010100&days=15&appKey=weather20151024&sign=zUFJoAR2ZVrDy1vF3D07&romVersion=7.2.16&appVersion=87&alpha=false&isGlobal=false&device=cancro&modDevice=&locale=zh_cn"];
        NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15.0];
        NSURLSession *session = [NSURLSession sharedSession];
        NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
            if (error) {
                NSLog(@"error - %@",error);
            } else {
                
                [weakSelf.cache setObject:data forKey:@"REQUEST"];
                NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];
                NSLog(@"dict -%@",dict);
            }
        }];
        [task resume];
    }