一般使用SDWebImage 进行图片的显示和缓存，一般缓存的内容比较多了就需要进行清空缓存

// 清理内存
[[SDImageCache sharedImageCache] clearMemory];


// 清理webview 缓存
NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
for (NSHTTPCookie *cookie in [storage cookies]) {
    [storage deleteCookie:cookie];
}


NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
[config.URLCache removeAllCachedResponses];
[[NSURLCache sharedURLCache] removeAllCachedResponses];


// 清理硬盘
[[SDImageCache sharedImageCache] clearDiskOnCompletion:^{
    [MBProgressHUD hideAllHUDsForView:self.view animated:YES];


    [self.tableView reloadData];
}];